HMS Unruffled was a Royal Navy U-class submarine built by Vickers-Armstrong at Barrow-in-Furness, and operated from April 1942 until being scrapped in January 1946.

[5] P46 slipped her moorings for the first time on 8 April 1942, under the command of Lieutenant John Samuel Stevens, and transferred to Holy Loch for sea trials.

[6] P46 departed Holy Loch on 13 May 1942, transferring to Lerwick where she began her first wartime patrol on 16 May, operating off of the North Sea coast of Norway.

A second victory was to come half an hour later, when P46 sighted the Vichy French merchant ship Liberia and torpedoed her, causing her to sink.

P46 shadowed Leonardo Palomba for just over an hour before engaging with torpedoes again, hitting the ship amidships and igniting her petrol stores.

[6] On her following patrol, P46 surfaced off the coast of Calabria in the early hours of the morning on 9 October, and opened fire on a passing train; two hits were observed, but damage was very light.

[6] A follow-up attack was mounted by HMS United, but she was unable to cause any damage, and Attilio Regolo was towed to dry dock, where she spent the rest of the war.

Following this she was attacked by an Italian aircraft dropping depth charges, which caused minor damage to P46, but ultimately she survived and returned to Malta on 18 December.

[6] In early January 1943 P46 accompanied Operation Principal, a frogman attack on Palermo, and recovered two crews after they deployed their Chariot manned torpedoes.

[6] On 26 January she engaged and sank the Italian Z 90 / Redentore with her three-inch gun; the crew were forced to abandon ship, and a boarding party from Unruffled found it already awash and sinking.

[6] The captain of the 10th Submarine Flotilla commented that this was a name "well suited to her commanding officer [Stevens]," whose judgement in intercepting SS Lisbon he commended.

An attempted counter-attack with depth charges proved unsuccessful, and Unruffled returned unharmed to Malta on 8 June.

Her next combat patrol began on 27 July, and saw the sinking of the Italian troopship Città di Catania as she entered Brindisi on 3 August,[1]: 105  having first unsuccessfully engaged the ship two days earlier.

She had on board two Greek officers, who she delivered to Cephalonia on 25 August to undertake sabotage missions as part of Operation Seaman.

Two days later she engaged and sank the Italian merchant vessel Città di Spezia with a full salvo of torpedoes.

[6] The RNSubs website identifies the ship as the German merchant Pommern, and suggests that Unruffled successfully torpedoed her, however this is not recorded in other sources.

[3] At some point in the post-war years, the plaque was lost, before being re-discovered and put back on display in Colchester Town Hall on 14 March 2012.