Some butchers in south London are trading in illegal meat which could cause mad cow disease, a BBC Watchdog investigation has revealed.
Meat sold in London was found to be "unfit for human consumption"
Three shops were selling the African delicacy smokies, a carcass blow torched with the skin and fleece on for a chargrilled flavour.
They are illegal because they are sold with the brain and spinal cord.
When confronted one butcher denied the allegation while the other claimed not to know smokies were illegal.
The investigation, which centered around three shops, revealed that part and whole smokies were being sold for up to £200.
One butcher sold a leg, spinal column and several cuts of smokie while another took a deposit of £60, promising to deliver a carcass in two days time.
A third butcher, after at first being suspicious, provided a whole smokie and two heads for £180.
The sheep are bought for as little as £10 as unfit for consumption or are stolen, many from Wales.
Julie Barratt, from the Chartered Institute of Environmental Health, said: "It's unfit from the start.... it's no better than pet food on legs.
"Every stage of this process is not just unlawful, it's fraught with risk.
"From the illegal movement of animals, to their being killed unlawfully, the illegal sale of them with the risks of cross contamination and unfit meat entering into the food chain.
"All those risks are risks to public health."
Dr Yunes Teinaz, Environmental Health officer and expert in illegal meat, examined a carcass obtained by Watchdog.
He said the sheep was very old and posed a "theoretical risk of BSE".
Dr Teinaz said the animal was a Welsh breed which was emaciated and "not fit for human consumption".