19 December 1941 - an history known by a few people that we (Italians) are proud of… 
Six Incursori (frogman raiders) of the X Flottiglia MAS of the Regia Marina (Royal Italian Navy) with 3 human manned torpedos, sunk in Alessandria harbour two British battleships (HMS Valiant and HMS Queen Elizabeth). One British destroyer and one Norvegian tanker were also damaged in the same operation.
In 1945 Bianchi and Durand de La Penne and the other frogmen that sunk the Valiant, have been decorated by the Italian Navy with the Gold Medal to Military Valour that was awarded to them by Admiral Charles Morgan, head of the Mediterranean Fleet and former commander of the HMS Valiant. The lives of 1.700 sailors of the Valiant crew have been saved by Durand De La Penne, prisoner on board of the Valiant, who informed the british battleship commander to abandon the ship a few minutes before the detonation.
In the following picture: while Prince Umberto di Savoia is going to appoint the medal to Luigi Durand de La Penne, Rear Admiral Charles Morgan is asking him “the honour to appoint himself, by that that simbol of courage, an Italian man of honour”
Read the history here:
Sinking the Valiant:
Luigi Durand de La Penne
Something interesting to be read:
“Sea Devils” by J. Valerio Borghese, translated into English by James Cleugh, with introduction by the United States Naval Institute ISBN 1-55750-072-X