Meantime a card arrives. The sorting office is holding a letter for me understamped by 4p, and for a £500 surcharge, I can pick it up.

The letter is from the Prime Minister, the Occasionally Honourable Gordon Brown. I assume the lack of stamps is part of the government cost-cutting exercise to help pay for two wars in Afghanistan and Iraq, the same philosophy that could soon close your local post office.

If in future you need an eight mile trudge to collect your pension, be confident it is in a good cause. As you set off, raise your fist to the heavens and shout "take that Osama Bin Laden! And let it be a lesson to you!" I guarantee you will feel better.

Meantime I slit open the letter from the PM to PM (haa, haa! My little joke!).

Dear Mortimer,

I am hoping you can help me. I have no idea who I can turn to, and approach you in a state of desperation. For some time now I have had this growing sense of panic. After only a short spell of office I realise I am a dead loss as Prime Minister. I was pretty good as Chancellor, where people seemed sympathetic to my dour demeanour. After all, people who look after the finances are expected to be dour. When did you last see an accountant dancing on a table top?

Anyway, most people thought I'd be good at the present job. Plus which, they were fed up with the grinning politics-lite of Blair.

But it hasn't worked out. Something has gone desperately wrong and I'm trying to find out what it is. What can I do about it?

Yours, Big Gordie.

How flattering he should write to me! Then I read the PS.

I hope you don't mind, I have sent this letter to 10,000 other people simultaneously.

Me, help the Prime Minister? His was the murky world of politics, the cut-and-thrust, spin doctoring society about which I knew nothing. Holding the reins of political power was something alien to me, despite once being a committee member of the Seaton Delaval Non-Sexist Leek Growers Society, (which is pretty impressive on the CV).

I wrote back:

Dear Gordon Brown/Prime Minister/Right Honourable member/Big Gordie, I know little about such things. Except I admire those who mix conviction politics and humour. Take Nelson Mandela, or Tony Benn. It's no good having one without the other. Conviction without humour means you end up like Hitler, Stalin, Genghis Khan, or Robert Mugabe, (none of whom has us slapping our thighs) and if the humour has no serious base, you become Boris Johnson. Maybe lighten up a bit, people might take you more seriously.

Yours, etc

The reply was swift.

Dear Mortimer,

Very well. I could tell a joke at PM's Question Time, which I hate. That awful David Cameron ribs me, or even worse, Vince Cable from the Lib Dems. You mentioned Stalin. Cable said I'd changed from Stalin to Bambi. People fell about, and his ratings soared! It is humiliating for me to sit there slack-jawed while MPs are guffawing at this kind of humour. But I seem to remember a joke my mother told me, while she added the salt to the breakfast porridge, and brought the bagpipes to the boil. Here goes. "I say, I say, my wife's gone to the West Indies!"
"Your wife's gone to the West Indies – Jamaica?"

"No, but my dog has no nose, and smells awful!"

Do you think that would get the critics off my back? Would it cause them to call my performance 'dazzling', and ensure I didn't become one of the shortest lived Prime Ministers in history?

I replied.

Dear PM,

The correct reply is 'No, she went of her own accord.' Why not practice the joke in front of the mirror, then tell it while announcing you're bringing the troops home? That might be a telling combination, and worth a shot.

By the way, did you know our Co-op's downsized?

Yrs...

PETER MORTIMER