Conversation so far:
where did madness (band) form?
North London.
Who was in the band?
Mike Barson (Monsieur Barso) on keyboards and vocals, Chris Foreman (Chrissy Boy) on guitar and Lee Thompson (Kix) on saxophone and vocals.
Who did they also recruit?
They later recruited John Hasler on drums and Cathal Smyth (better known as Chas Smash) on bass guitar.
Later in the year, they were joined by lead vocalist Dikron Tulane.
Who came back?
By 1978, the band had allowed McPherson to return, after filling in temporarily for Hasler.
when did he leave?
1977.

Question: Why was he there?
Self-contained rewrite: Why was McPherson in the Madness band.