The London bombings and the war on terror have put politics back into comedy at the Edinburgh Fringe Festival, according to the director.
The Edinburgh Fringe Festival gets under way on Sunday
Paul Gudgin said it was "rather exciting" that this year's Fringe was shaping up to be the most political since the 1970s.
Some comedians say they are re-writing their shows daily as events develop to keep in line with public mood.
The Fringe, featuring up to 1,800 shows, gets under way this weekend.
It became apparent very early on that there was a huge number of performers and artists who were desperate to talk about the war on terror and how the world is at the moment," Mr Gudgin told BBC One's Breakfast.
"It is the most dominant theme I think I have seen in the Fringe programme for many, many years."
Comedian Stewart Lee said he had to re-write his act after the bombings in London.
He said: "On 7 July, I was sitting trying to get my Edinburgh show together - and then the news started, and obviously everything changed.
"All of the material I used last year about the attitudes to Islam in the West, I couldn't use any more.
"It would seem naively optimistic and forgiving in the way everything has changed into a feeling of paranoia and fear."
Muslim comedian Omar Marzouk said he no longer had to tell jokes in his act, but just had to refer to his life which "has become very funny".
But Marzouk said some comedians had to remember there were limits, especially in the current climate.
"People who do not have a faith have completely different boundaries and feel it is OK to make fun of everything," he said.
"Being Muslim, there are things that are holy to me and I think others should respect that."
Mr Gudgin said audiences would quickly act if a comedian went too far.
"Word of mouth spreads around the city like wildfire at festival time and they will find their audience dropping off."
He added: "I think this is the most political Fringe we have had since the 1970s, when political theatre was all the rage.
"In some ways that is rather exciting."