"I can't think of any other drummer that would have fitted in so perfectly," says Steve Harris. "Nick plays the drums the way most guitarists play their guitars - he's riffing right along with you, note for note, I've never known anything like it! He doesn't just hold the beat, he drives the whole thing along, and as the bass player having to keep up with him every night, that's great for me. It means none of us is ever allowed to give less than 100 per cent."

Ask the great man himself, of course, and you get a more modest assessment. "Every drummer worth his salt has his own unique way of doing things," he says. "I just do what I do and, luckily for me, what I do sounds great in Iron Maiden."

It certainly does. Joining the band in 1983, in time to record the 'Piece Of Mind' album - still regarded by many, not least Steve Harris, as one of the greatest Maiden albums ever - it's impossible to imagine now what Maiden masterpieces like 'Where Eagles Dare', '2 Minutes To Midnight', 'Can I Play With Madness', 'Be Quick Or Be Dead' or ' Man On The Edge' would or could have sounded like without Nicko's full-spectrum drums thundering along behind them.

Playing live on stage though, is where Nicko has really made his larger-than-life presence felt. Clive Burr, his predecessor, was a fine drummer, too, and an argument could be - and often is - had over which of the two is, technically, the best. For most of us, Nicko wins hands down. But there's never been any doubt over who was the more entertaining stage personality. The Mad McBrain, as he has become known to the Maiden fans, is almost as freaky an on-stage presence as Eddie, leaping shirtless from his drum stool to lead the cheers as the band bound into another diamond from their bejewelled back-catalogue.

As for his off stage personality, "Mr Excess All-Areas," he once described himself as to me, and it's fair to say he wasn't exaggerating. I remember flying with him once from London, on our way to a record company party in Germany for what was then the new 'Seventh Son of A Seventh Son' album. We sat in First Class and Nick had already charmed the stewardesses into letting us have a jug of Bucks Fizz before the plane had even taken off. He then proceeded to hand out signed black- and-white photographs of himself on stage with Maiden. I'm not sure how many of the other Fist Class passengers - tired-looking businessmen, mostly - had heard of Iron Maiden before the plane took off, but they certainly had by the time we'd landed.

"I'm a born entertainer, me," Nicko laughed, and we all laughed with him because we knew it was true (and besides, we were onto our third jug of Fizz by then).

And yet, behind the laugh-a-minute facade, there is, after all, a real human being lurking. Michael Henry McBrain was born in Hackney, East London, on June 5, 1952. Don't laugh but he was, he cheerfully confesses, nicknamed 'Nicky' as a child, because that was the name of his favourite teddy bear - Nicholas The Bear. "I used to take him everywhere with me, and so my family just started calling me 'Nicky' for fun. Unless I was in trouble, then it was 'Michael!'"

His first experience of music came via his father's love of trad- jazz. Little Nicky's hero was Joe Morella, the late, great drummer with the legendary Dave Brubeck jazz band.

"I used to pretend I was Joe Morella hitting the tubs. I'd go into the kitchen and pick up a pair of knives and start hitting the gas cooker."

Fed up with him bashing up the kitchen utensils, his parents finally bought him a proper drum-kit when he was 12.

"Most kids wanted a bicycle or something like that, but all I wanted was drums. When my mum and dad finally got me one it was like all my birthdays and Christmases rolled into one!"

He says he seemed to be able to play "almost straight away - I don't know how, I just could." By the time he left school at 15, he was already a veteran of several part-time pub groups. Musically, however, his tastes had broadened to include more contemporary Sixties sounds and suddenly his dad's jazz collection was infiltrated by records from The Shadows, The Animals, The Beatles and the Stones. On the recommendation of another drummer he knew, he began to take on session work, playing on countless different recordings.

"I'd do anything - pop albums, folk albums, religious albums, or more rock type stuff, I didn't mind. It was all good practise."

His first 'proper' band was The 18th Fairfield Walk, who did covers of Otis Redding and Beatles tunes. Then he joined the Wells Street Blues Band, who were, in the lingo of the day, "a more purist blues thing". But again, they never got beyond the clubs and Nicko found himself meandering from gig to gig, playing with now barely remembered names like singer and keyboardist Billy Day (who first started calling him Nicko, as a joke), The Blossom Toes (also featuring guitarist, Jim Cregan, later of Cockney Rebel and Rod Stewart fame) and others.

It wasn't until 1975, when he joined Streetwalkers, the band formed by ex-Family members, vocalist Roger Chapman and guitarist Charlie Whitney, that Nicko first found any sort of fame.

"They were lovely fellas, Roger and Charlie, and the Streetwalkers was a great little band. Why they never made it, I don't know."

Unfortunately, the Streetwalkers was destined to be one of the great also-rans of the Seventies: good albums, no hits. From then until he joined Maiden, Nicko had been occupied mainly in session work, most memorably with the Pat Travers Band (on their 1976 'Makin' Magic' album), then with French soci-politico punk-metallists, Trust - who actually supported Maiden on tour in the UK in 1981.

Steve, however, remembered him from before that, when Nicko was playing in a three-piece called McKitty, who Maiden shared the bill with at an open-air festival in Belgium, two years earlier.

"I remember McKitty's guitar got fucked-up halfway through the set and Nick ended up doing this sort of solo jam thing while they tried to fix it. And he was just fucking amazing! I mean, I find drum solos pretty boring, but this was better than watching the rest of the set! Then when Clive left, Nick was one of the first people I thought of."

Of course, nobody - not even Nicko - is perfect, and he admits he has his "funny moods", as he calls them. "One minute I'm up and I'm Mr Party All Night! Then the next minute I'm down and I'm Mr Grumpy. But that's just the way it is. Maybe I need to do that sometimes to get myself psyched up for a gig. 'Cos believe me, the way I play - the way this whole band plays - you better be psyched up for it! Or you'll get left behind!"

And that's a promise...