Alexander was born in 1923 in Newton Abbot, Devon to Samuel and Kathleen née Barrett and had a younger brother Louis. Their father Samuel was a travelling cotton salesman. Samuel was born in Prestwich, Manchester and was previously married to Dora Cohen, and had two children Daniel and Maud ‘Alty’.

Alexander was the observer on Lancaster ED319 which departed RAF Scampton on a night operation to Essen. During the inbound flight over Holland they encountered Luftwaffe night fighters. The aircraft was intercepted by Lt. Erich Richter of 2./NGJ his second claim of the war. The aircraft crashed at Haarzuilens 12 km NW of Utrecht with the loss of all crew.

Pilot, Sgt. David Stanley Warlow, RNZAF, 414705
F/E, Sgt. Vincent John Mervyn Donaldson, 574813
Nav, Sgt. Alexander Jacobsen
A/B, Sgt. Robert Elwyn Roberts, 1389926
W/Op A/G, Sgt. Jack Webber, 1377524
A/G, Fl/Sgt. William Albert Gillen, RCAF, R/135059
A/G, Sgt. George Roe, 1576603