HMS Victorious was then chosen as flagship for Operation Pedestal in August 1942, being a no-holds-barred attempt to relieve the island of Malta.

Apart from her experience against FW 200 long-range reconnaissance aircraft in the Atlantic, she had previously covered Malta convoys as part of Force H, based at Gibraltar.

The operation led to the most intense sea-air battle against the Luftwaffe yet seen, and the first full-scale test of the recent improvements in the Royal Navy's fighter direction.

The chair tilted forward, and only a quick grab of each arm by C-in-C and the Fighter Direction Officer saved Churchill from a dive.

When, in September 1941, Borthwick joined one of the earliest courses at HMS Heron, the Royal Naval Air Station at Yeovilton, Somerset, fighter direction was in its infancy, and much of the training equipment improvised.

For "aircraft", the fledgling Fighter Defence Officers (FDOs) used commandeered Stop-Me-and-Buy-One ice cream tricycles which were pedalled around the airfield by Wrens who could not see where they were going and were directed to "intercept" on earphones.

He had asked for a telephone line to the radar office, but the captain wrote on his request: "Voice pipes are quicker and more efficient."

Victorious wore the flag of the Rear Admiral Aircraft Carriers Home Fleet for the Malta convoy Pedestal, one of the most spectacular operations of the war at sea.

On 10 August 1942, 14 merchant ships, among them the tanker Ohio, headed eastward through the Straits of Gibraltar, escorted by the battleships Nelson and the carriers Eagle, Indomitable and Victorious (and Furious, with Spitfires for Malta), seven cruisers, and 32 destroyers.

Borthwick and his staff handled the fighters with great skill over a very tense period of some days, generally managing to maintain Combat Air Patrols (CAPs) from dawn to dusk, despite losses.

He was called to the Bar by Inner Temple in 1933, but joined his family firm of Thomas Borthwick and Sons, meat importers, in 1934 and travelled extensively to Australia and New Zealand.

Early in 1940, Borthwick heard about a new Admiralty order that holders of the old Board of Trade Yachtmaster's Ticket could be interviewed for a commission.

By now one of the Navy's experts on fighter direction, Borthwick served on Admiral Ramsay's staff for the D-Day landings in Normandy in June 1944.

He was a director of International Commodities Clearing House Ltd, a member of the Central Council of Physical Recreation, and chairman of the National Sailing Centre at Cowes.