Walter Bast also regained the use of his right arm after the operation to place a 'teabag' of drug-producing stem cells in his brain.

Speaking a week after the operation  -  the first of its kind in the world  -  he said: 'I feel a lucky guy.'

If further trials prove the treatment's worth, it could be on the market in as little as five years, providing fresh hope for the 45,000 Britons each year who suffer a haemorrhagic stroke, where a blood vessel in the brain bursts.

Currently, the only treatment option is surgery, which has a variable success rate.

Half will die within a month and just one in 20 patients will recover to the extent of Mr Bast, a 49-year-old mechanic.

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British experts described the operation as 'very promising'.

The CellBeads treatment is the brainchild of scientists at the British medical technology firm Biocompatibles International, based in Farnham, Surrey.

At its centre is a teabag-like sachet filled with tiny capsules, each containing around a million stem cells.

The stem cells, taken from bone marrow, have been genetically engineered to make a drug that protects brain cells from dying.

This lets the cells rejuvenate and repair the damage done by the stroke.

The stem cells are encapsulated in beads to hide them from the immune system and ensure they are not rejected by the body.

Enclosing everything in the 2cm square 'teabag' ensures the surgeon can easily remove it at the end of the treatment period.

Mr Bast, who lives near Bremen in Germany, agreed to be the first to test the operation after suffering two strokes in quick succession. 

Doctors at the International Neuroscience-Institute in Hanover left the teabag in his brain for a fortnight while the stem cells pumped out the drug, known only as CM1.

Now, six weeks after surgery, Mr Bast's body has returned almost to normal.

His surgeon, Professor Thomas Brinker, said: 'We see a recovery as good as this in only the minority of patients, so it is an encouraging start. It is important that we found no side-effects.'

Dr Peter Stratford, of Biocompatibles, said a one-size-fits-all treatment could be stored in hospital freezers ready for use when required.

If effective, it could have a huge impact on patients' quality of life and save the NHS billions.

But stem cell scientists cautioned that many safety and ethical hurdles would have to be crossed before the treatment was accepted for widespread use.

Haemorrhagic strokes account for around 30 per cent of the 150,000 strokes in the UK each year.

Stroke is Britain's third biggest killer, after heart disease and cancer, and causes more disability than any other disease.

It costs the economy about ? 7billion a year, including NHS bills and lost productivity.