The RAF night raid on the German seaplane base on the Island of Sylt near the German-Danish coast on 19/20 March 1940, marked a decisive shift in the conduct of World War II. Until then, the RAF had been prevented from bombing military targets on land because of fears of civilian casualties. A German air attack on Scapa Flow on 16 March 1940, however, had purposely hit a nearby town, killing one civilian, and Bomber Command was ordered to retaliate. The operation is captured beautifully and dramatically in Raid on Sylt 19th March 1940 by marine artist Norman Wilkinson to be offered in Bonhams Marine sale in London on Wednesday 11 November. It is estimated at £30,000-50,000.

Raid on Sylt depicts the twin-engined Whitley bomber of Wing Commander William Staton silhouetted over the target, under a fierce barrage of German flak. A rare survivor of a band of Royal Flying Corps Bristol fighter pilots on the Western Front who duelled with Baron von Richtofen's deadly 'Flying Circus', Staton – known variously as 'King Kong' and 'Crack 'Em Staton' – was a larger than life character and perfectly fitted the media's idea of a gritty British hero. The day after the attack, the papers were full of his exploits and those of his men – only one of the 50 aircraft was lost, and the raid was hailed as a triumph. Raid on Sylt was commissioned by Wing Commander – later Air Vice Marshal – Staton himself and painted in 1940-41.

Bonhams Senior Picture Specialist, Rhyanon Demery, said: "Raid on Sylt is a striking portrayal of a significant escalation of hostilities during the Second World War. Despite the media reports, there is little evidence that the raid inflicted much actual damage, but it did provide a much-needed boost to public morale. It also revealed deficiencies in RAF navigation and bombing skills and the rapid changes to operational tactics that followed, proved their worth during the long, difficult years ahead."

Norman Wilkinson (1878-1971) was born in Cambridge. He studied figure painting in Paris and was a prominent oil, watercolour and drypoint artist. During World War I, he developed the Navy's striking dazzle paint schemes on their ships. His work forms part of a number of collections and galleries, including the Royal Academy, Fine Arts Society and Royal Society of Arts.