As noted in the first instalment of this story, Barnes Wallis had originally envisaged a streamlined ten-ton bomb that would bury itself in the ground creating a man made earthquake. Not feasible at the time it was shelved in favour of the development of the bouncing bomb. Now, with the Lancaster in service and improvements to the Merlin engine, Wallis’s attention returned to his original project. After satisfactory tests of a small scale 4,000 lb version, a 12,000 lb (six-ton)example was manufactured with the codename 'Tallboy'. It was 21 ft long and comprised a cast steel body and an aluminium tale section with off-set fins. After release the bomb very quickly adopted a nose down attitude and started to spin, reaching a maximum rotational velocity of 300 rpm before drilling into the earth, where it exploded. Unlike conventional bombs it was suspended in the aircrafts bomb bay by means of a heavy cast link chain with an electrical release unit. On April 22nd Flt Lt Dave Wilson and John Pryor along with Lt Nick Knilans ( an American serving with 617 Sq ) flew down to Boscombe Down to participate in trials with the new weapon, returning to Woodhall Spa two days later. Even as No 617 Sq were departing for Operation Taxable on the eve of D-day, the first 'Tallboys' had arrived at Woodhall Spa. Three days later on the 8th June, 617 Sq would use the weapon for the first time, against the Saumur railway tunnel and nearby bridges in the Loire region of France. This was a vital target as it was the main link from Southwest France for reinforcements heading for the Normandy bridgehead. On the evening of the 8th, 25 Lancasters, the largest single force deployed by 617 Sq to date, accompanied by 2 Mosquitos set out for the target. 19 Lancasters carried the only 19 'Tallboys' available, the rest ( including two of the original Dambusters ED909 / KC-P and ED933 / KC-N) being loaded with 1000 lb bombs. As it turned out this was the last time any of the former Dambuster aircraft would go into action. Once over the target Cheshire dived from 3,000 ft to 500ft dropping his markers on the embankment at the Southern end of the tunnel. Fawke in the other Mosquito dropped his at the Northern end, just as a train 'chugged' into the tunnel. The squadron began bombing moments later, smoke and dust from the first couple of 'Tallboys' soon obscured the target, but near misses were good enough. Both ends of the tunnel were collapsed but most impressive was a 'Tallboy' that bored through the hillside and into the middle of the tunnel. The train that had entered stopped in the middle when the raid began, it was loaded with munitions and took a direct hit from the 'Tallboy'. The resulting explosion completely blew out the side of the hill. Further down the line a bridge and large section of track were also put out of action. Poor weather curtailed most flying over the next several days, but this allowed the re-stocking of 'Tallboys'. On the 14th the weather cleared and No 617 Sq was given another important job. The supply line across the Channel to Normandy was under constant threat from E-Boats operating from Le Havre, putting their reinforced concrete base out of action was essential. For the first time in over a year No 617 Sq would be flying a daylight mission, carrying 'Tallboys' as part of a force of more than 220 aircraft. Once again Cheshire would lead and mark in his Mosquito, and they would be escorted by a squadron of Spitfires for protection,although in the event, no enemy aircraft were encountered. The flak however was very intense, with several aircraft damaged. Again Cheshire’s marking was spot on and although some ordinance from the main force fell on the town, No 617 Sq performed ‘in keeping with tradition’. One 'Tallboy' went straight through the 16 ft reinforced concrete roof and exploded inside the pen and in an instant the Le Havre E-Boat threat was gone.