He and his younger brother, Paul, 26, spent two years in jail awaiting trial for a stabbing he says they knew nothing about. They served six months in Modelo jail, the most overcrowded in Europe, sleeping on urine-soaked mattresses in a cramped cell shared with four other people. In those six months three people were killed in the jail. He witnessed a stabbing.
"It was a nightmare. I lost two-and-a-half stone. I was a vegetarian, living on apples. The drug problem in the prison was horrendous - about half the prisoners were said to be HIV- positive."
Mr Sell, 27, said it was only when their plight started attracting publicity that they received help from the British Consul."Until then he did not help us at all," he said.
The brothers, both builders from Ely, Cardiff, were moved to a better jail. But they still waited a further 18 months before finally coming to trial, after two aborted attempts when the Turkish prosecution witnesses failed to attend. Following a trial before a judge and no jury, the two were convicted of the stabbing, but freed because they had already served two years.
More than 2,000 prisoners will spend Christmas behind bars in foreign jails, many like the Sells, waiting for years to come to trial and many held in overcrowded, unsanitary conditions.
A study by Roger Matthews, of Middlesex University published today says these "forgotten" British prisoners are disadvantaged at every stage of the foreign criminal justice system - from legal services, the provision of bail, the operation of prison rules, trial delays and possibilities of early release or parole - because of inadequate support from embassy and consular staff. "These systematic disadvantages tend to prolong the period of confinement and intensify the pains of imprisonment," the study says.