Tears in Trafalgar Square as Harry Potter hangs up his wand

It wasn't just the fans camped in Trafalgar Square who shed a tearful goodbye to the boy wizard. The premiere of Harry Potter and the Deathly Hallows: Part 2 marked the end of a £2bn spell cast over the UK film industry.

From distinguished thespians to producers, special-effects experts, technicians and caterers, the Warner Bros franchise has kept the infrastructure of the national film industry in gainful employment for a decade.

The credits for the final film, produced at Leavesden Studios in Watford, list more than 1,100 names.

Warner Bros estimates that it spent about £2bn making films in Britain during the Potter decade, which generated eight instalments.

Described as "the biggest windfall in the history of the British film industry" by the UK Film Council, now axed under the Coalition's cuts, the end of the Potter cycle means uncertain times for a national movie business living in Hollywood's shadow.

Warner Bros has expressed its confidence in Britain as a production base by committing to invest £100m to expand Leavesden, a former Rolls-Royce factory.

The 170-acre site will be redeveloped to include a Harry Potter theme park, new sound stages and prosthetics, and animatronics workshops, which could generate 1,500 jobs.

Despite a squeeze on box office spending, the UK film industry is optimistic. Tax breaks, an improvement in post-production facilities and the continued glow from the Oscar-winning King's Speech mean that inward investment in the industry is tipped to exceed £1bn for the first time this year.

Adrian Wootton, chief executive of Film London, said: "The Potter cycle has ended but they have left a golden legacy in the crews we have developed and the investment in post-production skills and special effects.

"Warners is shooting the new Batman and Sherlock Holmes films here and we are using the Potter films as a sales tool to encourage Disney, Fox and the other studios to make movies here."

The UK tourism industry will also hope for a new franchise to replace a series which brought record visitor numbers to locations such as Alnwick Castle in Northumberland, the screen Hogwarts.

In Trafalgar Square, thousands of fans who had braved days and nights of rain to camp out in the hope of meeting the film's stars were rewarded with a break in the weather last night.

Some had travelled from as far as Argentina and Australia, and screamed as Rupert Grint arrived first before walking the mile-long red carpet to Leicester Square, where the premiere was screened.

Grint, who plays Ron Weasley, said it was "emotional" arriving to see the final film. Fans waved placards reading "Potter 'til I die" and "Harry Potter is over. See you in therapy".

Potter in numbers

£2bn Estimated spending in the British film industry by Warner Bros after eight films.

£604m Box office takings of the first, and most profitable film, The Philosopher's Stone, released in 2001.

£42m The fortune that Harry Potter actor Daniel Radcliffe is said to have amassed, still only aged 21.