Nicko McBrain has been
Iron Maiden's drummer since 1983.
Michael Henry McBrain was born June 5, 1954 in London. He got the nickname Nicky because he always carried his favorite teddy bear, Nicholas, with him everywhere he went. He kept the nickname (although it changed to Nicko) over the years. As a kid, he used to immitate Joe Morella, a drummer with the legendary Dave Brubeck jazz band, by hitting on pans in the kitchen. He got a real drum kit at age 12, because his parents got sick of him trashing the kitchen.
The 18th Fairfield Walk was the first real band Nicko joined, and they played mostly coversongs. After that, he played in lots of bands, includingStreetwalkers, with vocalist Roger Chapman and guitarist Charlie Whitney, who were his first band who had a bit of fame. Unfortunately for them, they never got their real breakthrough hit.
In 1976, he drummed on the Makin' Magic and Putting It Straight albums by the Pat Travers Band. He played in a small band called McKitty on a Belgium festival in 1979, where Iron Maiden were also playing. After that, he joined French band Trust, who opened for Iron Maiden during their 1981 UK tour.
When Clive Burr left Iron Maiden after 1982's Beast On The Road tour, Nicko was asked to fill in the spot behind the drum kit. He gladly accepted, and hasn't left the band yet, fortunately.
Even though he hasn't written any songs for Iron Maiden, he released one song of his own in 1990, Rhythm Of The Beast, with Dave Murray on guitars. It was done as part of his drum clinic tour he did in the UK, showcasing his skills to other (usually starting) drummers.
Sources: Official Iron Maiden fanclub newsletters, the official Iron Maiden website, various fan websites, various magazine articles.