|U-570 as HMS Graph undergoing sea trials|
Eureka, I have an answer.
The short answer to whether a captured German U-boat came up the Medway (namely U-570) is no.... The long answer is Yes she did....
Now bear with me on this one as I prepare to weave you a narrative about the ill fated U-570.
On April 15th 1941 the type VIIC U-boat U 570 was launched and commissioned at the Blohm and Voss ship yards in Hamburg where she immediatly began her shake down cruises and tests before reassignment to Norway where she took on her new crew and began training excercises with her inexperienced crew. She was then assigned to Trondheimsfjord and the Lofjord Naval base where she was part of the 3rd Flotilla.
Her Commanding officer Kapitanleutnant Hans-Jurgen Rahmlow was a seasoned naval officer with a history of commanding Coastal batteries and had only recently transferred to U-boats (although having briefly commanded the training vessel U-58), her First officer Bernhard Brandt had only been serving on U-boats for a few months, the Second watch officer had only just been commissioned and most of the crew were new recruits. The only man onboard who really had any experience was the Chief Engineer and three of the Petty officers!
German Naval intelligence picked up a sypher that there was a large convoy of Allied vessels passing to the South of Iceland and the Third Flotilla were assigned to attack them. U-570 slipped out of base on 24th August with orders to patrol the area South of Iceland before turning towards La Pallice base in France with provision for four weeks.
By the 27th August, her Captain ordered her to surface to give the crew some restbite as many were suffering from accute seasickness and a couple had become incapacitated. They were immediatly picked up on radar by an RAF Hudson of 269 sqdn flown by Sqdn ldr Thompson. Rahmlow heard the approaching bomber from the observation deck and immediatly orderred a crash dive. It was too late as four depth charges were quickly dropped and one exploded a mere ten yards from the U-boat.
The resulting explosion nearly rolled the vessel, shattered her instruments, she lost all power and sprang several leaks. The smell that was generated made the inexperienced crew think that water was getting on the batteries and filling the hull with noxious Chlorine gas. The order was given to surface and ten crew raced onto the deck, under machine gun fire, unable to man the Flak guns because of the rough seas they quickly hoisted the white flag of surrender.
The officers quickly reported what had happened to Navy command and calmly destroyed their radio equipment and code books. Donitz orderred U-82 to the area to assist but was kept at bay by Allied air patrols.
The crew were kept onboard, save for the wounded (from the first attack and the subsequent attacks mistakenly made by the Royal Navy warning shots and an aircraft of 330 sqdn) so that the Germans wouldn't sink her on purpose. She was taken to Iceland and beached.
By the 31st August Lieutenant Colvin RN and his team of engineers had restored power and bouyancy and the boat was sailed to Hvalfjorour where she spent three weeks under repair. It was discovered that the damage was not critical and that a more experienced crew would have been able to repair the damage and evade the attack - further compounded by the fact that the Hudson bomber had used all its depth charges in the attack and so would have lost the U-boat had she stayed submerged.
Along with her escorts HMS Saladin and HMS Kingston Agate sailed for Barrow-Foreness and arrived on the 3rd October 1941. There she was renamed and ceased to be U-570. She was rechristened HMS Graph.
HMS Graph went under extensive tests in Scotland to test her capabilities and also for training for boarding crews so that they could become acclimatised to finding their way around U-boats looking for enigma machines and reversing any scuttling damage.
On 25th April 1942 she sailed South to Portsmouth before departing for Sheerness. Then from there she sailed up the River Medway. Whether she sailed under the escort of a Sunderland or other aircraft for her own protection in case any errant gunner feared a U-boat was repeating Prien's attack on Scappa flow, is open to conjecture.
She finished her refit in Chatham on 14th August 1942 and is taken over by Lieutenant Marriot RN before sailing for Sheerness, Portsmouth (under escort of HMS Vesper) and on to Holy loch for training.
On 8th October 1942 she left Holy loch for her first war patrol to the bay of Biscay and on 21st she sighted the German U-boat U-333 and fired four torpedoes. Four explosions were heard and "breaking up noises"
According to the U-333's log she didn't even see Graph only a torpedo track go past her and she dived to avoid any further attack but remained unscathed.
Graph's other two patrols were fairly uneventful, though she was ordered on 29th November to intercept the Italian blockade runner Cortellazzo along with HMS Sealion and HMS Clyde and all three failed to sight her. On her final patrol she fired at a German destroyer and explosions were heard. This destroyer was part of the escort of the Cruisers Hipper and Lutzow however none of the vessels were sunk by Graph, and I've not so far been able to see if they were damaged.
After her final patrol she returned to Scotland. She sailed south once more to Chatham and arrived on 13th June 1943 before finally being handed over to Dockyard control on 21st June and used for training duties.
Sadly, with a lack of parts available (seeing as they were produced in Germany), the short life of the engines and the need to replace the batteries annually the Graph was no longer sustainable and in 1944 she was used for target practise and for tests to see what damage depth charges do, having survived all of this she was assigned for breaking up, towed by HMS Allegiance to Clyde for breaking up. The tow rope broke and the vessel beached near Coul Point. She has been partially scrapped in 1947 but parts were still visible in 1977 at low tide.
Thus ends the tale of HMS Graph/ U-570 and here brief tour up the Medway.
There is, however one last footnote that, personally I find interesting so will bore you all with now. After her capture Officers was taken to Grizedale Hall, a POW camp for German U-boat officers, where they were put on trial in an Honour court by the senior Germans present, including Otto Kretschnerr the U-boat ace. They were charged with cowardice in the face of the enemy and Rahmlow (en absentia) and Berndt were found guilty of cowardice. On the 18th October 1941 Berndt escaped the camp and was supposedly making his way towards Barrow (22 miles away) to destroy U-570 to redeem himself. He was caught by the Homeguard but refused to be taken, even ignoring warning shots and was unfortunately shot dead.
The British then put Rahmlow into a camp with Airmen and Soldiers for his own protection.