He met Miller at Cambridge in 1992 when they were both in the Cambridge Footlights. As well as co-starring in four series of Armstrong and Miller from 1997 to 2001, Alexander has performed in other comedy and drama and sitcom roles.
He appeared in Steve Coogan’s 'Saxondale' in 2006 as a famous motoring correspondent and as David Cameron in the satirical fictional documentary 'The Trial of Tony Blair'. He played a middle aged man who leaves his wife during a mid-life crisis in 'Maggie Mae' and appeared as a guest star in 'Hotel Babylon' in 2007. He was the voice of Mr Smith, an alien computer, in 'The Sarah Jane Adventures' and in the 'Doctor Who' episodes 'The Stolen Earth' and 'Journey’s End'.
He’s possibly best known for his starring roles in the Pimms adverts, and his successful chairing of the BBC’s satirical panel game 'Have I Got News for You' and also regularly appearing as a guest on the programme.
His TV presenting career includes chairing the comedy panel show 'Best of the Worst' on Channel 4 which features team captains David Mitchell and Johnny Vaughan.
He presented the ITV1 comedy quiz series 'Don’t Call Me Stupid' and in 2008 was presenter and narrator for all twelve episodes of 'When Were We Funniest?'
He is presenter of the 2009 BBC2 game show 'Pointless' and also presented the 2009 BBC documentary 'Alexander Armstrong’s Very British Holiday'.