'So, Eddie Izzard, were your marathons an attempt to trump my swims?'

DAVID WALLIAMS: I asked on Twitter if anyone had any questions for you and someone wrote “Is he still doing that gay tranny thing?” so I thought I'd just ask my own questions... I've always thought one thing about you is that you're fearless. Is that right?

EDDIE IZZARD: No, I'm fearful. About everything: dogs, helicopters. I am as fearful as the average person but I realise that it's linked with being a transvestite in a way. The moment I walked out that door in heels and make-up, in 1985, it was a red-letter day. I did feel I could say to the world: “Look, I'm a straight transvestite.”I don't know why I'm straight, I should be bi.

DW: But seeing me this morning, does that change anything?

EIi: Being straight? No. Why? You're 70 per cent straight and 70 per cent gay anyway. Anyway it was that pushing back of the fear. Who dares wins. It's like I wanted to be in the SAS.

DW: I'm interested in the fearlessness because you did 190 marathons in 28 days.

EI: You know I didn't do them really. I swam them.

DW: There's something about being a comedian that means you have to not be scared of failing because failing is part of the process, right?

EI: People talk about fear management a lot. I'm into fear compression. It's the control of your fear. I learnt to fly. I earned a pilot's licence because I was scared of flying and threw up on planes when I was younger. It took five weeks of intense work. Just little planes.

DW: So when you took on the marathons, was it purely to make me swimming the Channel look a little pathetic?

EI: No. You kicked me into action.

DW: Were you running already?

EI: A bit. But not long distances. Ten miles was the longest. I make decisions and then I can't stand dilly-dallying so I wanted to do it.

DW: I heard you were going to do another challenge, running barefoot in South Africa. And you were going to do it when I was swimming the Thames. I thought you were going to trump me again.

EI: I wasn't trying to trump you! I didn't know you were doing the Thames. I can't announce it yet but I am going to do another challenge. Up until I was 13 I was very athletic and then not at all. They didn't even play football at my school. And I love football.

DW: Do you have a team?

EI: Crystal Palace. And England. I grew up with it. You can support CP and England. When Europe plays the Ryder Cup, I'm pro-Europe. If the world was playing Mars at football, I'd support the world.

DW: Sport is the safe place we can be tribal?

EI: Yes, without the killing at the end. And you saw that great support for the footballer who had a heart attack. I think football can really help the world because it spreads the dignity around. You know, the dignity deficit, and why the guy set fire to himself in Tunisia that started the Arab uprisings. There's a lack of dignity in people's lives. You must feel a certain amount of dignity because you've got to a place, you've pushed hard, things have worked for you.

DW: I feel completely undignified every day.

EI: We have the potential in the UK to get to a place where they feel that things are going well for them. In some countries they don't have the chance; it's not going to happen. That guy who set fire to himself had a degree and was selling flowers and so he set fire to himself. That's what football can spread round the world. In the end you want people to belong to the tribe of human beings.

DW: So you're a number of tribes?

EI: CP, England, Europe, northern hemisphere, the world.

DW: You've become involved in politics. And when I last spoke to you, you said you were campaigning for Ken Livingstone. Is there a part of you that's concerned that if you get involved with politics, people will groan?

EI: Yeah, they do.

DW: You don't mind the groaning?

EI: I feel if I hadn't done entertainment I would have done politics. I'm planning to run as either Mayor of London or an MP in 2020.

DW: Would you really want that? There's already a comedian doing that job.

EI: I will try and do it sensibly. Boris thinks it's all about waving and handshakes. If people know what I've done with my life, I'm pretty serious. When I just did comedy people thought I was off with the fairies but now they know I came out as a transvestite, I ran 43 marathons, I do gigs in French, I played the Hollywood Bowl; people can see that I'm a driven little bugger. You can do positive things – raise money, help some people and do something positive for London.

DW: Would you do any of your duties in women's clothing?

EI: Oh yes. I'd have two looks.

DW: So will you be the Labour candidate in 2020?

EI: That's what I hope, yes. I could be up against some very talented other Labour politicians.

DW: Do you think Ed Miliband will win the next election?

EI: I hope so. I'll support him fully. I didn't support one candidate during the leadership campaign. I said whoever became leader I would support.

DW: I can't see why anyone would want to be in politics because you get so much criticism. We get criticism for not making people laugh but they get so much. And it's really personal.

EI: I agree. I do wonder, because I'm coming from a place where a lot of people are giving me the thumbs-up to a place where people are going to be giving me a hard time.

DW: And you always leave office in disgrace.

EI: Only Prime Ministers, usually.