But the book's authors believe that detailed contemporaneous notes of Soviet intelligence documents provide the solid proof that MI5 never found. The notes were compiled by Mr Vassiliev, who was invited to inspect KGB files shortly after the Soviet Union's collapse, when the intelligence service felt under pressure to prove that it had scored major coups. Mr Vassiliev then smuggled his notes to the USA in 2001, since when he and fellow researchers have conducted detailed cross-checks which they claim leaves no doubt as to who Eric really was.