from naval-history.net
Late November/early December - Royal Navy Submarines “REGULUS” and “TRITON” were lost in late November or early December, possibly mined in the Strait of Otranto area at the southern end of the Adriatic Sea. Alternatively “Regulus” may have been sunk by Italian aircraft on 26th November.
3rd December - At anchor in the poorly defended Suda Bay, Royal Navy cruiser HMS Glasgow was hit by two torpedoes from Italian aircraft and badly damaged.
North Africa - Gen Wavell launched the first British offensive on the 9th December 1940 against the Italian forces in Egypt. Sidi Barrani was captured on the 10th and by the end of the month British and Dominion troops had entered Libya for the first time. The offensive continued until February by which time El Agheila, half way across Libya and well on the way to Tripoli, had been reached. Italian losses in men and material were considerable. Units of the Mediterranean Fleet including the small ship Inshore Squadron and the Australian Destroyer Flotilla played an important part in supporting and supplying the North African land campaign. On the 13th December , cruiser HMS Coventry was torpedoed by Italian submarine “Neghelli”, but remained operational .
14th December - Also operating in support of the land campaign, destroyers “Hereward” and “Hyperion” sank Italian submarine “NAIADE” off Bardia, Libya just over the Egyptian border
Mediterranean Operations - Another series of convoy and offensive operations were carried out by the Royal Navy Mediterranean Fleet with battleships “Warspite”, "Valiant "and carrier “Illustrious”. On the **17th December carrier aircraft attacked Rhodes and on the night of the 18th/19th December the two British battleships bombarded Italian held port Valona on coast of Albania. At the same time, battleship “Malaya” passed through to the west for Gibraltar. On the way, escorting destroyer “HYPERION” hit a nine near Cape Bon, northeast tip of Tunisia on the 22nd December and had to be scuttled. “Malaya” carried on to meet up with Force H. The German Luftwaffe’s X Fliegerkorps - including Ju87 Stuka dive-bombers - was ordered to Sicily and southern Italy to bolster the Italian Air Force.
Mediterranean Theatre after Seven Months - A total of nine Royal Navy submarines had been lost since June in the Mediterranean, a poor exchange for the sinking of 10 Italian merchantmen of 45,000 tons. Most of the submarines were the large, older boats transferred from the Far East and unsuited to the waters of the Mediterranean. In the same time the Italians had lost 18 submarines from all causes throughout the Mediterranean and Red Sea areas. Mussolini’s claimed domination of the Mediterranean had not been apparent. In spite of the loss of French naval power, Force H and the Mediterranean Fleet had more than held the Italian Navy in check. Malta had been supplied and reinforced, and the British offensive in North Africa was underway. Elsewhere, the Greeks were driving the Italians back into Albania and away to the south the Italian East African Empire was about to be wound up. However, it was now only a matter of months and even weeks before the Luftwaffe appeared in Sicily, Gen Rommel in North Africa and the German Army in Greece, followed by Paratroops in Crete