British intelligence sought to suppress the investigation into a feared assassination attempt on the Second World War Polish leader General Wladyslaw Sikorski, according to secret files made public today.
Papers show that investigators never got to the bottom of the incident involving a incendiary device on a flight by Sikorski and his entourage from Scotland to Canada in 1942.
The incident happened just 16 months before Sikorski was killed when another aircraft he was travelling in crashed on take-off from Gibraltar.
The earlier incident, in March 1942, involved Wing Commander Bohan Kleczynski, an officer in the Free Polish Air Force, who claimed to have found the incendiary device "smouldering" among some blankets on the British Liberator aircraft.
Kleczynski said that he disabled the device by breaking off the fuse, which he threw into the aircraft's lavatory. He then pocketed the rest of the bomb "as I did not want to disturb the commander-in-chief unnecessarily".
When forensic tests proved that the device could not have been smouldering in way Kleczynski claimed, he changed his story.
This time Kleczynski, who was a bomber pilot, said that he had been given the device in 1941 on a visit to a Polish parachute school in case he was forced down in enemy territory and wanted to destroy his plane.
When he realised he had brought it with him on the flight with Sikorski, he panicked.
MI5 acknowledged that his second account was no more convincing than the first, admitting it was "not entirely satisfactory" and had "certain gaps in it".
