What was your grandfathers name, for reference?
it will help us track things down for you.
this is from January that year, Flight magazine:
8,000-mile Training Flight
SIX aircraft of the K.A.F. Central Navigation School left Shawbury on January 24th for an 8,440-mile training flight to Khartoum, returning on January 31st. Navigated by students of the specialist navigation course, they were to fly by way of Gibraltar and Cyprus, and return via Malta. The longest stage of the flight, the 2,250 miles from Gibraltar to Nicosia, Cyprus, would take 11 hours and be flown at night to allow celestial navigation.