He told BBC Radio 4's Today programme that it depends on a number of factors including:
- How the body has been buried
- What condition it was in when it entered the ground
- How expensive the coffin was
- Whether modern embalming techniques were used
He said: "I think it is certainly possible that they could find residual traces of radioactive material," but added it was doubtful they would find solid evidence of poisoning if only bones remain.
More top news
Ramona Marquez, Daniel Roche and Tyger Drew-Honey, who starred alongside Hugh Dennis and Claire Skinner, have been pictured together again.
'Why are Ucas sending me tampons?' one university-wannabe asked as dozens more took to Twitter over the unusual correspondence.
His mother Princess Diana was killed in a car crash in Paris in 1997 when he was just 12 and his brother William was 15.