Elton John in for Lily

Sir Elton John will perform at his Aids fund-raiser this weekend - after Lily Allen pulled out due to illness.

The Smile singer - who's pregnant - has a viral infection, but can't take medication due to her condition.

Instead, Sir Elton will treat guests to a 45-minute set at the winter ball on Saturday.

Lily's been advised to rest - and has apologised.