So he just disappeared in 1939/1940. The implication being that he was involved with the IRA bombing campaign at that time. Wikipedia gives a list
1939
* January 16: a bomb exploded outside the control room of a large power station, which supplied the whole of south-east England with electricity. It created a large crater in the forecourt of the building. There were no casualties and the control station was reportedly undamaged. A second explosion damaged an overhead cable running from Grand Union Canal to Willesden Power Station.
* January 17: a bomb exploded at Williams Deacons Bank, damaging gas mains.
* February 4: two bombs exploded in the London Underground – one at Tottenham Court Road station and one at Leicester Square station. They were timed suitcase bombs stored in the left-luggage rooms overnight. There were no deaths, although two people were wounded and severe damage was done to the stations.
* February 9: two bombs exploded at King's Cross station.
* March 2: a bomb exploded on an aqueduct for the Grand Union Canal near Stonebridge Park.
* March 23: five bombs exploded at different times during the day. Targets included telephone and gas installations, and the offices of the News Chronicle in Fleet Street.
* March 29: two bombs exploded on Hammersmith Bridge.
* March 31: seven bombs exploded in different parts of the city.
* May 5: two bombs exploded.
* June 10: bombs exploded in thirty post offices and postboxes in London, Birmingham and Manchester.
* June 24: several bombs exploded before or after a republican demonstration (under police protection) demanding the release of IRA volunteers.[4]
* June 24: bombs exploded at the London branches of the Midland Bank, Westminster Bank and Lloyds Bank.
* July 26: two bombs exploded in the London Underground – one in the left-luggage area of King's Cross Station and one in the left-luggage area of London Victoria station. In the King's Cross attack, one man was killed and two wounded. In the Victoria Station attack five were wounded.
1940
* February 6: two bombs exploded in mailbags at Euston Station.
* February 23: two bombs exploded in the West End. The devices had been placed in litter bins. Thirteen people were wounded.
I'll have a root round in the Times to see if I can track down a trial - or if anyone else finds it can they post it here