I want us to ping out from the solar system and if necessary to zoom through a wormhole, as they do in this new film Interstellar, in search of a heavenly Eden. I want our species to get up to Mars, at least; but that is not the objective of the Branson “spacecraft”. It is not about exploration; it is about luxury. It is about taking a very few people about 60 miles up and then giving them the sensation of weightlessness. The whole thing is to be over in four or five minutes and it costs about £250,000 per passenger. The mission is profoundly uninstructive about space, but it tells us a lot about the growing wealth gap here on good old Earth.

Now, I am not remotely anti-wealth. I don’t mind if people want to blow their fortunes pretending to be astronauts, not least because their investment will support a great many jobs – just as the Virgin group as a whole supports thousands of jobs. I don’t mind if the likes of Sir Richard Branson accumulate such vast sums that they can play around with space exploration. In fact, I think it is a tribute to his enormous enterprise and chutzpah.

There he is, a British businessman, valiantly filling a gap in the market that has been left by the relative timidity of Nasa. His project is a triumph of free-market capitalism, and I support the capitalist system in the sense that we have yet to find a better way of satisfying human wants and creating useful employment.

But the mere fact that some people are willing to spend hundreds of thousands of pounds for a few minutes in space is a reminder that there are millions of people who couldn’t even afford to take a taxi, millions who have difficulty paying for the bus or the Tube – and in the past 30 years, the gulf between the two income groups has been growing.

If free-market capitalism is capable of sending a rich person to space, then it can surely do a little bit more to help those at the bottom of the economic ladder. In many sectors of the UK economy – and not just in banking – we have seen the growth of “top people’s pay” outstrip the rest of the market.

All kinds of good reasons will be advanced for this: the need to reward talent, to remain competitive in a global market etc. But there is absolutely no reason why prosperous firms should not simultaneously give a little bit more to their lowest-paid employees.

That is why I so passionately support the Living Wage. Today, we unveil a new rate for London, and new firms are signing up the whole time. Google will confirm that it is joining the movement, and we are in talks with some of the biggest supermarkets – firms that have always been wariest about making the switch.

There were just 27 organisations that could claim to pay the rate when I became mayor; and I am proud to say that in spite of many annual uplifts, there are now 408 firms and other bodies that pay at least £8.80 per hour to all staff. These include banks, building societies, cinema chains, coffee shops, building contractors, pubs, universities, travel agents, accountants, galleries, local councils, charities, architects and many more. They have all seen the logic.

It is partly about putting tens of millions into the pockets of some of the poorest families in London, of course. But the firms that pay the Living Wage – and they do so entirely voluntarily – will confirm that it pays for itself: in lower absenteeism, in greater loyalty and productivity in the workforce.

I know that there are some free-market diehards who will say that London wages should find their own level – just as they might rigidly defend a Mauritius sweatshop that pays its female workers 62p per hour to make Ed Miliband and Nick Clegg their T-shirts, the ones that say “This is what a feminist looks like”.

These ideological purists should remember that it was Winston Churchill who first proposed such a measure in this country, when he said: “It is a national evil that any class of His Majesty’s subjects should receive less than a living wage in return for their utmost exertions.”

And the policy is surely deeply Tory in that it is rewarding those who work, those who make an effort – the people whose daily struggle is essential for allowing the wheels of the London economy to turn.

The Living Wage is starting to snowball, and deservedly to gather pace. Conspicuous among those that have yet to sign up is the Virgin group. May I respectfully suggest to Sir Richard that being known as a Living Wage payer would be even better for his brand than being known for sending rich people briefly into orbit.