The Prime Minister welcomed Mike Thornton, the new MP for Eastleigh - but only for the duration of this Parliament.
Two Lib Dem MPs - Martin Horwood and Sir Bob Russell - asked Mr Cameron about the Eastleigh by-election, and both tried to have a bit of fun at the Prime Minister's expense.
More top news
Tuesday's weather for the east with Philippa
Tuesday's weather for the west with Philippa
Thousands of bikers head to Hastings for a biking festival that organisers say now rivals the Isle of Man's TT races