Comedy challenges taste and convention, and it can arouse strong reactions, as we saw at this year’s Oscars when a joke earned Chris Rock a slap in the face from Will Smith. Stephen Sackur speaks to Omid Djalili, who has spent more than 25 years finding laughs in sometimes unlikely places. He was born in London to Iranian parents, and has thrived as a cross-cultural comedic chameleon. Is it possible to be funny without being mean?