It's not always easy keeping a grip on reality. Take a friend of mine. He's an actor, 6ft 4in, blue eyed, dark haired - an alpha man, the type you'd refuse to go swimming with in public. Recently, he spent six weeks in a gym, four hours every day, pumping iron. In the end, his muscles became so inflated I was afraid of approaching him with anything sharp.

All of this was in preparation for the lead role in a new 'hard-hitting police drama' - only to find himself struck out at the last moment. The producers didn't think he was 'real' enough. They wanted to show the metropolitan blues as they actually are: grimy, fraying and heavily tarnished.

'Wouldn't have happened in Jack Lord's day,' grumbled my friend. 'He played a cop you could really believe in.' He's got a point - with Steve McGarrett on the case, we could all rest easy. He always got his man. I remember when I was eight, I wouldn't go anywhere without my Hawaii Five-0 walkie-talkie and personalised Five-0 indentity badge.

It was disaffection with the dour, gritty, NYPD Blue repeats on TV that led me on to the balcony last week. Or perhaps it was the sound of children playing in the street below. And perhaps I should have been looking down on those children with a misty-eyed nostalgia for lost simplicities. But I wasn't. I was wondering at my innate suspicion of children playing in a street. That was until one of them smashed a car door window and pulled out the radio. Then I didn't feel so bad.

So, before you could say, 'Book him, Danny]', I was doing a Starsky down my stairwell out on to the street and sprinting after them like Clint Eastwood in The Enforcer.

When I finally cornered two in an alleyway, instead of casually throwing away a 'Do you feel lucky, punk?' line, I caught my breath to wheeze: 'Right, you're nicked]'. Having explained I was making a citizen's arrest, instead of cowering under the weight of my assumed authority, they just laughed. Watching them scurry away, I could only shout, 'Wait, you can't do that]', as if they'd just broken the game rules in a primary school playground.

Then the real police arrived. Not that they had much more success. Laden down in heavy wool trousers, sweat-soaked white nylon shirts and Trumpton-style helmets, progress over the walls and fences of suburban London was ploddingly slow. Finally, a garden gate collapsed under the weight of one of them, sending him sprawling and leaving me with the unexpected community service of trying to put the gate back together again. And as I watched the officer fish his helmet out of a pond and pick the duck weed from its badge, I thought that my friend's producers were probably right - this is how it really is.

Remarkably, the boys were caught. Apparently, two plain clothes CID officers picked them up nearby. They wanted me to come down to the station and give a statement. I steeled myself to be taken to some rat-infested, granite monolith where I'd have to go on a witness protection programme just to be saved, like Assault on Precinct 13, from the boys' parental vendetta.

What I found was almost as unsettling: a brand new, open-plan development. I was led through matt- black security doors into a stark, white, modernist cubicle with wall- to-wall two-way mirrors and left with a Rombouts filter coffee and a copy of the glossy in-house magazine, The Job. However, it was only when the CID officer arrived to take a statement that I was rendered speechless. He was 6ft 4in, blue-eyed, dark haired . . . the type of superman Barbara Cartland regularly whips up.

When his partner arrived, starched white T-shirt tucked into her perfectly faded 501s, and told me they were off for a quick tandoori, I was left wondering where I might find my old Five-0 identity badge and if I could possibly tag along.

'It's a funny thing,' one of them explained as I followed them to the entrance, 'but the only reason we were in your area was because they were shooting a film nearby.' It turned out some sort of hard-hitting police drama was being made. 'I'm thinking of going back tomorrow.' The officer laughed. 'You never know, they might offer me a part.'

I didn't give much for his chances. Tanned and coiffed, he may have been the genuine article but, from my experience, in the dour, gritty world of the modern police drama, they'd never believe he was for real.