Its duck-like head and body are mountain-sized celestial icebergs, left over from the formation of the earth and the solar system 4.5 billion years ago.

It is suspected that comets brought most of the water to earth, laced with carbon molecules that transformed into life. A successful landing on Wednesday will allow Rosetta to make an inventory of the molecules on 67P. Together with measurements made from the main spacecraft, this is hoped to reveal life's primordial ingredients.

Taylor won the top scientific spot on the mission in the summer last year. This made him the new kid compared with those who had been there since day one, more than 20 years ago. The role was quite a departure from his previous expertise studying the physics behind the aurora borealis, or northern lights.

"Scientifically we were taking a chance," says Professor Mark McCaughrean, senior science adviser at ESA, who appointed Taylor. "We discussed that he'd have to come up to speed very quickly in order to be able to develop credibility and gain the trust of the Rosetta science working team."

Taylor was asked to introduce himself to the rest of the team, and needed something to convince that he was not some kind of usurper. So he made them a promise. If Rosetta successfully roused itself from hibernation, he would have the mission tattooed on his leg.

It woke on schedule in January and there is now a YouTube video of Taylor receiving the ink from tattoo artist PriZeMan, a friend from school days. Rosetta has captured people's imagination more than any previous ESA mission. After giving a public lecture in Lisbon in September, Taylor was swamped with people wanting his autograph.

"When you step back when you interact with the public you suddenly get this realisation that this is a big deal," he said.

Taylor is no Oxbridge boffin, pluming his way through conversations with lashings of received pronunciation. Nor does he affect a transatlantic Nasa accent that ends up sounding more like Alan Partridge. Instead, think geezer with a PhD.

He is from Manor Park, north-east London. His father, a bricklayer, was convinced his son could do better and impressed upon him that physics would be a good subject because it was "the science of everything".

Earning places at University of Liverpool and then Imperial College, London, for his PhD in space plasma physics, Taylor worked with his father on building sites during the holidays.

"That was good motivation," he says, "Spending three months slogging my guts out made me realise that I wanted to go back to university and study hard."

Now a father, he says even his children have taken notice of what he is doing in his job.

At home, Taylor cooks to unwind, though his wife, Leanne, says it's because he likes eating. They have been together since the sixth form. "I have known him through all his incarnations: extremely long hair, short bleach-blond hair, bald head and his current relatively normal do," she says, adding, "But he is terrible at following directions, and has lost cars in multistorey carparks many a time.

"So, thank goodness Rosetta has one of the best flight teams in the world behind it. They have steered the spacecraft on a 10-year chase through the solar system to rendezvous with the comet."

When the landing attempt takes place on November 12, the washing machine-sized Philae will drop for more than seven hours before attempting to secure itself to the comet.

There is no chance of human intervention. It is so far away that a radio signal takes almost half an hour to arrive at earth, and then another half an hour for the response to travel back. Everything must be automatic, or, as Taylor puts it: "It really will be a case of see ya later lander, stay in touch."

On touchdown, Philae must harpoon itself to the icy surface or it will bounce off into deep space. Once secure, the lander will transmit a signal back to waiting scientists on earth. This is expected to arrive at 4pm (GMT) but what if it never comes? A momentary glitch, a chance collision with a boulder or an bad touchdown could all destroy Philae.

In contemplating such scenarios, Taylor grows serious.

"We have done everything we can to make it work. Now we have to wait," he said. "I'm positive that it will work - until it doesn't. As soon as we edge into that window of when we expect the signal, every moment we wait will be stressful. I admit that I am really not looking forward to that. It's the brown trousers time."