2 Commando and two men of the Norwegian Armed Forces in exile who were part of the Special Operations Executive.

Crossing the North Sea by submarine, on arrival in Norway they attacked and damaged the plant, which was closed for the rest of the war.

The second group was captured; one man died of wounds and the other seven were taken to Germany, interrogated and then executed at Sachsenhausen concentration camp.

Churchill told the joint Chiefs of Staff to propose measures for an offensive against German-occupied Europe, "They must be prepared with specially trained troops of the hunter class who can develop a reign of terror down the enemy coast".

2 Commando were Company Sergeant Major Miller Smith, Lance Sergeant Richard O'Brien, Lance Bombardier William Chudley and privates John Fairclough, Cyril Abram, Eric Curtis, Reginald Makeham and Fred Trigg.

[11] During the planning the commandos were supposed to be picked up after the raid by a Short Sunderland flying boat but this was cancelled before the mission due to the risk to the aircraft.

They also carried two compasses (one sewn into each collar tab) a hacksaw blade, a fighting knife and a Colt M1911 pistol.

The submarine left the Orkney Islands at 11:40 on 11 September 1942, under escort in British waters by HMS Sturgeon, Tigris and Thunderbolt.

[13] Junon crossed the North Sea undetected and near Glomfjord, rose to periscope depth and discovered that a fishing boat was trailing them.

[10] The commander of the raid, Captain Black, had decided against a frontal assault since he suspected any German defences would expect one.

A German topographical party was in the area and its commander, Leutnant Wilhelm Dehne, had spotted some unidentified figures above the Glomfjord.

On their approach they detected a small craft on the fjord; fearing they would be spotted, they decided to postpone the action and return to camp.

The commandos were running short on supplies and Black ordered the attack to proceed the following night, 19/20 September, no matter what.

Reaching their objective, they planted plastic explosives in a round pattern to blow a 3 ft (0.91 m) hole in the pipes.

The commandos in the power station discovered that the Germans had left the control room and only a Norwegian engineer was on duty.

Sergeant Smith and Private Fairclough were detailed to plant their explosives among the machinery in the powerhouse and the other commandos located the area where the Norwegian staff worked and slept.

Granlund left to look again but returned to the hut soon after, being unable to find it in the dark at the same time as Houghton and the other Norwegian, Djupdraet.

The second group were discovered by the Germans who opened fire, wounding Houghton in the right arm; surrounded, they were forced to surrender.

The O'Brien group split up, Granlund setting off by himself; they eventually reached Sweden without further incident and all four were repatriated by aircraft to RAF Leuchars.

The unwounded prisoners were sent to Colditz Castle and put into the solitary confinement, where Black managed to make contact with Flight Lieutenant Dominic Bruce RAF (known as The Medium Sized Man) giving him and others their names which were passed on to MI5 in London.

[18] Bruce was the last British person to speak to Black; on 13 October 1942 they were taken to the SS-Reichssicherheitshauptamt (RHSA) headquarters in Berlin, where they were interrogated one by one by Gruppenführer Heinrich Müller.

[29] The Brookwood memorial is for men and women of the British and Commonwealth armies who died during the Second World War and have no known grave.

[30] The German commander in Norway, Generaloberst Nikolaus von Falkenhorst, was captured after the war and tried by a British military court, for his part in carrying out the Commando Order.

Found guilty on all eight charges of urging the forces under his command to kill men captured in commando raids or handing prisoners of war over to the Sicherheitsdienst (SD) for execution, he was sentenced to death, which was later commuted to life imprisonment.