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.
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The 22 year old man is seriously injured in hospital. Police believe a baseball bat and iron bar may have been used in the attack