London - An extradition treaty between Brazil and Britain was formally ratified yesterday, but it is unlikely to mean a swift return home for Great Train Robber Ronald Biggs. Mr Biggs has been living in Rio de Janeiro for the past 27 years since his escape from Wands- worth Prison in 1965. Lawyers for Mr Biggs say the Brazilian Supreme Court had accepted their argument that Mr Biggs (68), could not be extradited because the 15- year statute of limitations for his 1963 crime had expired under Brazilian law.