All right, you can call off the search party. Everyone can go home. I've found him.

We have all been looking for a man to lead Labour's MPs, a proper leader to take the place of the current Coca-Cola League Two incumbent. And the answer has been right here all along, under our noses.

He has popular appeal, the media likes him, he's good on television and has deep roots in the party. He was a Glasgow Labour councillor and fought the Glasgow Hillhead seat for the party as far back as 1970. James Purnell hadn't even been born then. Now it is true he's getting on a bit and, yes, perhaps he's a bit left-wing.

But I think Vince Cable would be ideal. Brilliant thought, no?

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BACKGROUND

• Lib Dem rock star is incredible, incontrovertible, in-Vince-able!

• Lib Dems: Britons are 'obsessed' with property

• Clegg has room for improvement

• Is Darling dancing to Cable's tune?

On behalf of the Queen and myself, we'd like to thank you, Mr Brown, for your service to the country. And Sarah too, naturally. We hope this silver tea set will give you both much pleasure in your years of retirement.

There is, of course, a tiny problem with my otherwise flawless Vince Cable plan. You may have spotted it. But in case you haven't; irritatingly the man isn't at present a member of the Labour Party. Don't worry though, I've thought this through completely, I promise you, and I have come up with a cunning plan even better than one of Baldrick's.

You see it is perfectly obvious, isn't it, that we have one party too many. It is quite clear that one whole set of officers, fundraisers, party conference organisers and spin-doctors could simply be done away with. The more I look at it, the clearer it is. We don't actually need the Labour Party at all. We should merge it with the Liberal Democrats. Bingo! Vince and Rachel waving from the doorstep of No10 promising to bring harmony where once there was discord.

And let me add one more thing that might not be entirely clear by this point. I am dead serious about this plan. I may be the only one who is, and I don't think, ahem, that I am in an ideal position to execute it, but nevertheless, I am dead serious.

So let me tell you how I arrived at the idea.

I wonder if you have noticed a rather odd phrase pop up in the speeches of both Tony Blair and Gordon Brown. The phrase is “progressive century”. And, despite appearances, it isn't just a bit of speechwriter's twaddle; it is a real thought with some history behind it.

What both men mean by the “progressive century” is that the Conservatives dominated the 20th century, and in the same way, the “forces of progress” should dominate the 21st century. Mr Blair was the first person to use the phrase, but he did not think of it himself. It was passed on to him by Roy Jenkins. The idea entered Mr Blair's speeches during that odd period when the former leader of the SDP was acting as the Prime Minister's mentor.

Jenkins, however, didn't come up with the “progressive century” by himself either. He took it from his friend and inspiration, the brilliant left intellectual David Marquand. Which is fortunate, because it means that there is an entire book explaining what the phrase means.

In his 1991 book The Progressive Dilemma, Marquand noted that the in the 20th century the Conservative Party had so far spent 60 years in power. At the time of the Liberal landslide of 1906 such Tory dominance seemed unlikely. And a number of Conservative historians have observed that for ten years after that victory the Liberal offering seemed so potent that the Tories struggled to find a response.

Then, as Marquand tells it, came tragedy for the Left. It split. A new party emerged commited to two things that the Liberals refused to endorse - the power of organised labour and socialism. The split was not inevitable. The Liberals might have offered their support to the unions, the effort to commit Labour to socialism might have failed. But inevitable or not, the split happened. And the result has been years of Tory hegemony.

The reason for this dominance was not the split itself. It was that the Labour Party turned out to be based on two duff ideas. As Edmund Dell demonstrates in his wonderful book A Strange Eventful History, democratic socialism was founded on a spectacular misunderstanding about the world. Its proponents seriously believed that they could easily control everything while still being democratic. Throughout its entire history Labour has been backing away from a programme that was entirely impratical.

And then there were the unions. Don't get me started about the unions.

By the end of the last century, the Labour Party had abandoned both democratic socialism and the unions. This made it more sensible. It also made it entirely pointless. The split between the Liberals and Labour ceased to serve a useful function. If one was abolishing Britain's most annoying party it would, no question, be goodbye Lib Dems. But Britain's most unnecessary? Definitely goodnight and thank you, Labour.

Mr Blair understood this. He used the phrase “progressive century” for that very reason. He wanted to abolish his party while none of its members was looking, and replace it by one merged with Paddy Ashdown's Liberal Democrats. Then he lost his nerve. He thought that John Prescott might get cross and, with a huge majority, he couldn't be bothered dealing with a cross Mr Prescott.

And so an important opportunity was missed. The Liberals could have become the Labour Party of the south, hoovering up Tory seats in places that Labour could not win. Instead, Nick Clegg is turning them into the Tory Party of the North, winning Labour seats in places where the Tories are miles behind. Tactically for the Lib Dems this is smart, almost irresistible. Strategically for the Left as a whole it is terrible.

It seems that the progressive century may have to wait a while. And so will Vince and Rachel.

daniel.finkelstein@thetimes.co.uk

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