Armando Iannucci: Why do I want to change the system? The answer really is as simple as 1, 2, 3

AV is not complicated unless you call counting to three complicated. It's more modern and sophisticated

I've tried to keep out of the political debate about AV in case my appearance cheapened it any further. There's been such a proliferation of D-list celebrities in these discussions that at one point it looked like we were being asked to choose between voting Yes for Eddie Izzard or No for Rik Mayall. Alas, the media is hungry for fresh angles. In the last few weeks the same news outlets running stories about how ridiculous it is that politics is being run by celebs have been the very ones refusing to print or broadcast arguments for Yes or No unless they're given by non-politicians.

And so here I am. I still feel it's rude of me to harangue you into telling you how to vote. That's your decision, and I hope you go out and make it. All I can do is outline the reasons why I'll be voting Yes to AV and be done with it.

First past the post did work, once. In the 1950s and 60s, when up to 95 per cent of people voted either Labour or Conservative, it was the perfect, most effective way to get strong government. But for the past 40 years, that 95 per cent figure has declined. Nowadays, probably not much more than 60 per cent of the electorate votes for the two largest parties, with the rest fragmented among Green, Liberal Democrat, Ukip, nationalist and the like. Add to that the steady decline in the number who vote at all (possibly because fewer people feel there's a party that fully reflects their views) and we as an electorate now have a system that cannot cope.

The No campaign says that under AV we'll get more coalitions: the truth is, under first past the post, we're going to get more coalitions anyway. Most current opinion polls point to further hung parliaments. Would it not be best, in that situation, to at least have a modern voting system that can cope with that, and that can, at least, return MPs who have won the support of at least 50 per cent of their constituents?

David Cameron says we should keep first past the post because it's "fair, simple, and decisive". But in the past 40 years it has not been fair: twice we have had parties come second in the vote but first in the number of seats. And remember how first past the post gave America and the world George W Bush in 2002 even though he polled a million fewer votes than Al Gore.

First past the post is also NOT decisive. Cameron claims it gives us the ability to kick out unpopular governments. Wrong again: we've just come through 18 years of unpopular Conservative government supported by on average 38 per cent of the population, followed by 13 years of increasingly unpopular Labour government supported by 35 per cent. First past the post makes it more difficult to get rid of unpopular government.

Ah, but it's simple, says Cameron. Try explaining that to anyone on election nights, when complex swingographics show us how tiny 1 per cent swings in either direction can lead to huge majorities or hung parliaments. The implication is that AV is complicated. It's not. Unless you call counting to three complicated. That's all it is. You list your candidates in order of preference, and only as many candidates as you want. You can just list one if you want. AV is not complicated; it's sophisticated. There's a difference. It's more modern.

AV determines more accurately which is the strongest candidate by selecting the candidate who is first to get over 50 per cent. When so many of us feel powerless, when we feel real anger and frustration over issues such as NHS reform or tuition fees, when we nurture resentment that we're just not being listened to, isn't it better to have a system of electing our MPs that means our MP knows he or she will have to win the support and trust of at least 50 per cent of their constituents?

For too long, MPs, knowing they just have to get one vote more than their nearest rival, have concentrated on their core support: those housing estates in one district of their constituency, those suburbs in another, but not both. Under AV, an MP has to get to know their whole constituency, and learn to keep their support. An MP becomes more answerable to more of the electorate under AV.

But don't take my word for it; take David Cameron's. He was elected under AV. All party leaders were. Cameron is drawing up legislation to elect police commissioners under it. He has troops in Afghanistan fighting to maintain a democracy where voters list their candidates in order of preference. We list candidates in order of preference in Scotland, Wales, Northern Ireland, London and European elections. It is actually a profoundly British thing to do.

From 1832 onwards, British history has seen small but significant changes to our voting system, each one opposed by the establishment at the time, and each one proving popular once in place. I'll be voting Yes to AV to keep that modernising going. After all, we prefer houses to caves and cars to penny-farthings. Is it too much to ask for a more-up-to-date voting system as well?

Armando Iannucci is the creator of 'The Thick Of It'