I mentioned Harlesden Job Centre Plus a few days ago. The area next to this (the old service station site) is going to be redeveloped soon with a much smaller building than proposed in the past. The Job Centre itself is huge in comparison. The reason for its enormous scale (compared to the rest of High Street Harlesden) is that it is on the old site of the Willesden Hippodrome. As the Willesden Hippodrome (destroyed by bombs in the War) was so big, the replacement building could be big.
By the way, hippodrome is one of those words that have completely changed their meaning. Willesden Hippodrome meant a music hall. In the classical world, a hippodrome was an arena for horse racing. Greek for horse being "hippo".