Locale hero: Meet the location manager who can find the perfect spot for a TV murder

It's one of the most vital jobs in TV, but you won't get a Bafta for it… Gerard Gilbert spends a day with Nick Marshall, the location manager behind a new British adaptation of The Bridge

Each spring Bafta holds its crafts awards to honour the backstage professionals working in film and television. Everyone from editors to hair and make-up artists, costume designers to soundtrack composers and lighting directors has their own categories – everyone, that is, except arguably the most hard-working and multitasking of them all. Or as the ex-wife of one location manager put it to me: "You know what they say about location managers – first to arrive in the morning and the last to leave at night".

The location manager and his or her team of scouts and assistants have been called 'the forgotten department' – although Nick Marshall, location manager on such movies as The Girl with the Dragon Tattoo, Dustin Hoffman's directorial debut, Quartet, and Oliver Hirschbiegel's recent biopic about the late Princess of Wales, Diana, doesn't seem to mind. "I quite enjoy being part under the radar," he says, standing on the roof of a disused building in the centre of Oxford. Marshall has been busy since five o'clock that morning, 'dressing' a scene for the Inspector Morse prequel Endeavour, to be shown next year, in which a body will be thrown on to the streets below.

With four series of Lewis also under his belt, Marshall is an old Oxford hand, but it was a rather more challenging job in a TV murder mystery that I wanted to discuss with him. The Tunnel is an Anglo-French version of the Scandinavian drama The Bridge, in which a corpse is discovered exactly midway on the bridge joining Denmark and Sweden – except that in this Sky Atlantic remake, the victim's body is found halfway across the Channel Tunnel.

Eurotunnel having given their permission to film on their Folkestone premises, it was decided that the other locations should be in the vicinity – either on the Kent Coast or northern France. Enter Marshall. One of five location managers, the 47-year-old was responsible for the final three episodes, his job (fairly obviously, perhaps) beginning with what's actually written in the script. "However, I was given a degree of freedom to interpret locations," he says. "For example, there was one location referred to in the script as 'a sub-station'. But it wasn't necessarily a sub-station that was required – it was more a question of finding a unique building that would offer us the scale for what was needed."

In the end, Marshall found an early 19th-century redoubt – one of the forts built all along this stretch of Channel coast to fend off Napoleon – and it was while reconnoitring the redoubt that Marshall was able to employ another invaluable tool of his trade. "While I was looking in Dover, the vice-chairman of the local preservation society said, 'Personally, I would have a look at the redoubt in Dymchurch'." Marshall followed his advice, and it's the Dymchurch redoubt that appears in The Tunnel. "Tapping into local knowledge is always good," he says. "Although invariably you're having to kiss a lot of frogs before you hit the jackpot."

Just how many frogs is illustrated by his work on Diana: 60 different locations were used, many for minor scenes, but still requiring the whole production to move lock, stock and barrel – or rather catering trucks, talent trailers and portable toilets. On top of that, for each location, Marshall has to offer the director and the production designer a list of alternatives. "Of the 60 locations we used on Diana, I might have offered 15 to 20 options," he says. That's around a thousand potential locations to be sifted for just one film.

With four series of Lewis also under his belt, Marshall is an old Oxford hand (John Lawrence)

Three separate buildings stood in for Kensington Palace in Diana, a task made harder by the fact that the original is a Christopher Wren building (a working knowledge of historical architectural style is a must in this line of work). Owners – or the National Trust and English Heritage, which have their filming departments, as does the Ministry of Defence and the City of London (the publicly-funded Film London) – are approached early on, but the discussion only turns to money later. "The fee will be dictated to by the budget of the programme," says Marshall. "As a general rule, the location manager will propose so much for filming days and 50 per cent of that figure for any preparation and re-instatement days."

Can he be more specific? "OK, so for a standard television drama in a standard stately home, you'd expect to be paying in the region of £2,500 a day, and half of that for preparation and re-instatement days. That's quite modest for a decent stately home – in fact there's one I'm filming at the end of this week that's costing me just over £5,000 for a day's filming."

It makes you wonder how much the Earl and Countess of Carnarvon, owners of Highclere Castle in Berkshire – aka Downton Abbey – are raking in over Downton's five-month annual shoot, although the sums don't always add up for landlords. The proprietors of a disused former Catholic missionary college in Mill Hill, north London, where BBC1's Call the Midwife has been filmed, this year decided to redevelop the site as luxury flats – meaning that the 1950s-set drama has had to relocate its main production base to Surrey.

Costs can spiral when filming in a pub or restaurant. "Breweries are usually reluctant to sacrifice their usual business for filming so, for pubs, you tend to look for free houses," says Marshall. "Then you have to buy out the potential loss of business, invariably with a bit of a mark-up as a location fee… staff costs come into it as well… and so it goes on." Does he ever see dollar signs in the eyes of those he approaches? "With some people, yes."

Marshall can't disclose how much, if anything (the free publicity must be priceless), Eurotunnel was paid to film at their terminal in Folkestone and in the service tunnel between the two railway tracks, although this unique filming opportunity brought its own logistical problems. "The level of security we hadf to adhere to in order to get in there was akin to getting air-side at Heathrow airport," he says. "We had to give names, places of birth, dates of birth and passport details of every cast member, crew member and extra in advance of any filming, and then we had to provide passports on the day. But it was worth it in the end."

Also, once it was decided to dispense with a studio nearer to London and to film everything on location, Marshall had to find private homes nearby, as well as securing Howletts, the wild animal park near Canterbury founded by John Aspinall. The scouting process might sometimes involve the production designer and the director jumping into the Volvo XC90 off-roader that also operates as Marshall's mobile office – although movie directors tend to be less available for these recce adventures than the TV variety. Dustin Hoffman, for example, didn't join in the scouting for Quartet. "In Mr Hoffman's case," says Marshall, "the director is so well known that he needs more protection than driving around in a car with me."

The Tunnel is an Anglo-French version of the Scandinavian drama The Bridge (Sky Atlantic)

The job isn't all about stately homes and big-name directors, however. Alex Gianopoulos, the location manager on 2013's most-discussed show, Breaking Bad, told a reporter from the techie website HunchMag, that that particular show has taken him to "some pretty sketchy places". "I keep finding myself talking to weirdos on the street while I have an expensive camera hanging around my neck," Gianopoulos says. "But in the end I knock on the door of a crack house the same way that I ring the gate of a mansion. Honestly, I sometimes find that the more ghetto area of town is more friendly than the wealthy."

Nick Marshall's two nastiest moments were when scouting for an inner-city pub and finding himself in a thoroughly unwelcoming hostelry on a Sunderland housing estate – and when he sneaked over the fence to recce a disused school in Southall, west London, and found himself face-to-face with the Rottweiler guarding the place. Luckily, the dog was in a good mood that day and "escorted me off the premises".

Until his early thirties, Marshall was by his own admission "a staggeringly unsuccessful actor" on the lookout for a career change. His older sister's partner, a lighting gaffer, was about to start work on an ITV drama called Daylight Robbery, when Marshall undertook his own smash-and-grab raid and asked whether the location manager needed an extra pair of hands. "And thankfully he did," he says. "I was a location assistant. Then after a couple of jobs I was asked if I'd be interested in stepping up to unit managing [dealing with all the practical issues on location, from parking to placating angry neighbours] and after three or four jobs, somebody very kindly offered the job of location manager on The Inspector Lynley Mysteries. I've been getting up at five in the morning ever since."

A relative newcomer to the job is 25-year-old Louis Cooper Robinson, a freelance location assistant whose most recent assignment was scouting for a mobile phone commercial. He studied sociology at Bristol University, although it was his pastime as a semi-professional skateboarder that proved the more useful training. "For the past 10 years I have been forever looking for spots where I could go skating," he says. "So I have that knack of finding locations, searching the streets… the kind of drive to keep looking till you find something – that works."

Cooper Robinson, like Marshall, started out as that general dogsbody of the film world, a production assistant. "Then two different location managers took me on board as their personal assistant," he says. "And from there I got shown a bit of scouting, and scouted on my first film, Still Life [which starred Eddie Marsan], a film with 50 locations and I did 25. I love having a bit of creative input into the overall shot. A lot of the job is logistics, but the way the shot is set is a very visual thing."

He works as a freelancer, and he's also on the books of Salt, a 'one-stop' location management company that also has an extensive database of potential venues to browse. Looking for a Palladian manor house rectory within easy reach of the M25? Click and ye shall find. Marshall has his own database which one day, when he's not so busy, he'd like to put into some sort of order. "I've been doing this for 14 years, but the hours are so long that, in terms of a nine-to-five job, it's been more like 25 years."

Another useful tool of the trade is Google Earth, says Breaking Bad's Gianopoulos. "If I'm looking for swimming pools or parking-lots, then Google Earth is priceless," he says. "But when I need something like an 'Exterior two-story house, with little to no bushes in front, near the Vamanos Pest [the fumigation company in Breaking Bad]' location, the best way to do it is to walk up and down every street in the vicinity."

"Google Earth?" muses Marshall. "Funnily enough, it's actually very useful if you're looking for parking." Ah, parking – a key logistical matter that can invade even his off-duty moments. "I remember I was in Cornwall with my wife once and I showed her a particular car park that I thought was splendid and she looked at me disdainfully and pointed out that I was showing her a car park and I should just relax. I can't speak for all location managers, but I'm a bit like a hamster on a wheel."

'The Tunnel' begins on Sky Atlantic, this Wednesday at 9pm

Belgium's Stadhuis doubled-up as Westminster Hall in the BBC drama The White Queen (BBC)

DRAMATIC VENUES: TV'S FINEST LOCALES

Owned by the Carnarvon family since 1697, Highclere Castle faced a £12m maintenance bill in 2009. Chosen as Downton Abbey, its fortunes turned around as visitor numbers increased.

Built in 1871 as a seminary to train priests, St Joseph's College in Mill Hill, north London, was used to recreate the Nonnatus House convent of Call the Midwife. Chummy Browne and her co-nurses are now looking for a new home, as the £25m building is to become luxury flats.

The famous 221b Baker Street is in fact 187 North Gower St, with amended door furniture. The flat went on the market last year for £330 a week, but for any prospective tenants hoping to find remnants of Sherlock's Cumberbatch, interior scenes were shot in-studio.

Belgium's Stadhuis was built in 1376 and has been the seat of city government ever since. Fans of BBC drama The White Queen will recognise its incredibly detailed Gothic interior as the 15th-century Westminster Hall that plays host to the schemings of Rebecca Ferguson and Max Irons.

BY OSCAR QUINE