Bigger than ordinary lambs and with as much as 10 to 20 per cent more lean meat, the flock bred with a mutated gene looked to be the diner's dream.
But Dr Wolf, animal scientist at the University of Wales, Aberystwyth, and his colleagues have hit a snag. Although the 50 lambs they have reared are much heavier, more meaty and less fatty, some of the meat is just a bit too tough.
They were bred with a mutated gene called callipyge, taken from the Greek and meaning beautiful buttocks, a reference to the enhanced size of the back legs and loins.
"Our work with them finishes in the autumn when we will be putting them through the abattoirs. At present, they are too tough for the British market and I think my colleagues will be eating a lot of lamb later this year," said Dr Wolf.
The gene, which is responsible for a double muscling effect, was found by American researchers in a flock of Dorset sheep. Some sheep at Aberystwyth were impregnated with semen containing the gene.
"The effects on the carcass are remarkable. Normally, you get 55 percent lean meat from a lamb. With our sheep you get an animal which is bigger and 63 per cent lean," said Dr Wolf.
"The changes seem to occur at four to eight weeks. They are born normally and as far as we can tell they don't eat any more than an ordinary sheep, they simply use it more efficiently and have more muscle than fat.
"The one adverse effect, so far, is that the meat from the loin region in particular tends to be tough - and that is the area where lamb chops come from."
There are ways of tenderising meat, for example by using the chemical calcium chloride. But there are worries that such procedures might harm the image of lamb, which is still highly regarded by consumers and has not been hit by a BSE scare or controversy over factory farming.
Dr Wolf says that various way are now being looked at to soften up the meat. "If these are successful, there could be enormous prospects for the future," he said.
Meanwhile, researchers are looking at whether the gene has any effect on the behaviour and welfare of the animals.