HMS Orchis (K76): The First Radar-Equipped Corvette, Sunk on Juno Beach a Week After Her Finest Hour

The First of Her Kind

HMS Orchis was built by Harland and Wolff and commissioned on 29 November 1940, a Flower-class corvette that earned a particularly significant place in naval technological history barely three months later: in March 1941 she became the trials ship for the prototype 271X set, declared fully operational that May, the first ever fitting of the new Type 271 radar, a centimetric set capable of detecting a surfaced submarine at 5,000 yards and even a submarine's periscope at 1,300 yards, a notably revolutionary leap in capability that transformed the Royal Navy's ability to detect U-boats at night or in poor visibility, conditions under which submarines had previously enjoyed a considerable advantage. Its distinctive wedge-shaped parabolic aerial, housed in a rotating perspex dome to keep the weather off, earned the set two nicknames among the sailors who had to live with it: "the Cheese" for its shape and "the Lighthouse" for the way its beam swept round.

It is worth saying why nobody had managed a set like that before, because the answer is one of the great British inventions of the war. Radar up to 1941 worked on wavelengths measured in metres, which meant big aerials and a beam far too coarse to pick a conning tower out of the clutter of the sea. To see something that small you need a wavelength of a few centimetres, and to get a useful radar out of a few centimetres you need to generate a great deal of power at that wavelength. Nobody could.

On 21 February 1940 three men at the University of Birmingham, John Randall, Harry Boot and James Sayers, got a resonant cavity magnetron to work. It is a block of copper about the size of a fist with holes drilled in it, and theirs put out more than four hundred watts at a wavelength of 9.8 centimetres. The same device, scaled and cheapened, is in every domestic microwave oven in the country.

Britain had it and could not manufacture it at scale, so in September 1940 the Tizard Mission carried a working example across the Atlantic in a black box, together with very nearly every other British military secret worth having, and handed it to the Americans. One of them wrote afterwards that they had brought over "the most valuable cargo ever brought to our shores".

And thirteen months after that first reading in a Birmingham laboratory, a Flower-class corvette working out of Greenock was carrying the first operational set built round it, and could see a periscope at thirteen hundred yards on a black night. The U-boat's great advantage, which was to run on the surface after dark where nothing could see her, ended aboard HMS Orchis.

Escorting the Atlantic Convoys

HMS Orchis initially served with the 4th Escort Group based at Greenock, before transferring to Escort Group B3 of the Mid-Ocean Escort Force. In September 1943 she was one of five B3 Group escorts, alongside HMS Keppel, Escapade, Towy and Narcissus, screening the combined Convoys ONS 18 and ON 202 when German U-boats renewed their North Atlantic offensive using the T-5 "Gnat" acoustic torpedo, a new weapon designed specifically to home in on an escort's own propeller noise, for the first time on any real scale. The escort group held its nerve and kept the convoy largely intact, though not without cost: HMS Itchen of the supporting 9th Escort Group was torpedoed and lost, taking her commanding officer, Commander Bridgeman, down with her, exactly the kind of gruelling, high-stakes convoy work her pioneering radar had been designed to make safer.

Sinking U-741

HMS Orchis was reassigned to English Channel patrol duties as the focus of the naval war shifted towards supporting the Normandy invasion, and on 15 August 1944, under her new commanding officer T/A/Lieutenant Commander Bryan Webster Harris DSC RNVR, achieved a genuine and confirmed success. Southwest of Brighton at 50°02'N, 00°36'W, she gained sonar contact on the German submarine U-741 and sank it with a pair of Hedgehog attacks followed by depth charges, a textbook demonstration of exactly the kind of detection-to-destruction sequence her class had been built to carry out.

She rescued one survivor from the U-boat's aft torpedo room, a small mercy amid the violence of the engagement.

Lost to a Mine Off Juno Beach

HMS Orchis met her own end less than a week later, on 21 August 1944, when she struck a naval mine off Courseulles-sur-Mer that destroyed her bow section back as far as the 4-inch gun mounting.

She was beached on Juno Beach, one of the Normandy invasion beaches assaulted by Canadian forces on D-Day some ten weeks earlier, and was declared a total loss, a painful and swift reversal of fortune for a corvette that had, only days before, scored one of the more satisfying confirmed kills of her entire wartime career.