railway tunnel were collapsed by Tallboys dropped by 617 Squadron. William Reid's Lancaster at was hit by a 'friendly' Tallboy dropped from . Sorties against German dockyards Shipping in the English Channel and the Atlantic Ocean were threatened by U-boats and E-boats stationed in France. U-boat docks were protected against conventional aerial bombardment by thick concrete roofs. 14 June 1944 – Le Havre Part of the first massive RAF daylight raid since the end of May 1943, two waves attacked E-boat facilities at Le Havre: No 1 Group first, No 3 Group second. Just before the first wave, 22 Lancasters of 617 Squadron and 3 Mosquito marker aircraft attacked, several hits were scored on the pens, one bomb penetrated the roof. 15 June 1944 – Boulogne harbour 297 aircraft: 155 Lancasters, 130 Halifaxes, 12 Mosquitos, of Nos 1, 4, 5, 6 and 8 Groups attacked Boulogne harbour. One Halifax was lost. A French report described the great destruction as the worst raid on Boulogne. During the raid 22 Lancasters of No. 617 squadron bombed the E-boat pens with Tallboys. Due to cloud cover ten planes returned to base with their bombs. However, the raid was considered a success as the E-boats retired to IJmuiden on the Dutch coast, where they were better protected but less able to interfere with Allied naval traffic supporting the Normandy invasion. 5 August 1944 – Brest 15 Lancasters of 617 Squadron attacked the U-boat pens at Brest and scored six direct hits with Tallboys, penetrating the concrete roofs. One Lancaster was shot down by flak. Subsequent attempts to reinforce other sites with even thicker concrete diverted resources from other projects. 6 August 1944 – Keroman Flight Lieutenant Thomas Clifford Iveson dropped one Tallboy, bomb failed to penetrate base. 7 August 1944 – Lorient The planned Tallboy mission against the U-boat pens was cancelled, Instead Keroman Submarine Base was the primary target. 8 August 1944 – La Pallice Flight Lieutenant Thomas Iveson dropped one Tallboy. 28 August 1944 – IJmuiden Iveson dropped one Tallboy. September – November 1944 23/24 September 1944 – Dortmund-Ems Canal near Ladbergen, north of Münster During the night attack 617 Squadron scored six direct hits with Tallboys. 7 October 1944 – Kembs Dam north of Basle The dam waters could have been kept in reserve to flood the area of a US advance. The Dambusters destroyed the lock gates with Tallboys dropped