The world's first test-tube burger, made from lab-grown meat, has been cooked and eaten in London.

The 142g (5oz) patty, which cost £250,000 to produce, was prepared by its creator before an invited audience.

Scientist-turned-chef Professor Mark Post produced the burger from 20,000 tiny strips of meat grown from cow stem cells.

He believes it could herald a food revolution, with artificial meat products appearing in supermarkets in as little as ten years.

Prof Post's team at the University of Maastricht in the Netherlands conducted experiments which progressed from mouse meat to pork and finally beef.

He said: "What we are going to attempt is important because I hope it will show cultured beef has the answers to major problems that the world faces."

He said: "Our burger is made from muscle cells taken from a cow. We haven't altered them in any way. For it to succeed it has to look, feel and hopefully taste like the real thing."

Prof Post is confident he can produce a burger that is almost indistinguishable from one made from a slaughtered animal.

He believes that livestock farming is becoming unsustainable, with demand for meat rocketing around the world.

Unveiling the research last year at a science meeting in Vancouver, Canada, he said: "Meat demand is going to double in the next 40 years.

"Right now we are using 70% of all our agricultural capacity to grow meat through livestock. You can easily calculate that we need alternatives."

Multi-step process to turn stem cells into burger

A multi-step process is used to turn a dish of stem cells into a burger that can be grilled or fried.

First the stem cells are cultivated in a nutrient broth, allowing them to proliferate 30-fold.

Next they are combined with an elastic collagen and attached to Velcro "anchor points" in a culture dish.

Between the anchor points, the cells self-organise into chunks of muscle.

Electrical stimulation is then used to make the muscle strips contract and "bulk up" - the laboratory equivalent of working out in a gym.

Finally the thousands of beef strips are minced up, together with 200 pieces of lab-grown animal fat, and moulded into a patty.

Around 20,000 meat strands are needed to make one 142g burger.

Other non-meat ingredients include salt, egg powder, and breadcrumbs.

Red beetroot juice and saffron are added to provide authentic beef colouring.

A major advantage of test-tube meat is that it can be customised for health, for instance by boosting levels of polyunsaturated fats, said Prof Post.

Manufacturing steaks instead of minced meat presents a much greater technical challenge, requiring some kind of blood vessel system to carry nutrients and oxygen to the centre of the tissue, he added.

The animal welfare organisation Peta (People for the Ethical Treatment of Animals) welcomed the research.

A spokesman said: "One day you will be able to eat meat with ethical impunity.

"In-vitro technology will spell the end of lorries full of cows and chickens, abattoirs and factory farming. It will reduce carbon emissions, conserve water and make the food supply safer."