As the campaign against French factories continued, 617 Sq attacked the Michelin & Cie Tyre Factory near Clermont Ferrand. The factory consisted of three large workshops and a workers canteen, again the emphasis was on accuracy to eliminate the possibility of civilian casualties. Once again Cheshire began by flying low to warn workers, before releasing his markers on the factory roof. Bombing was so accurate, the three workshops were completely destroyed but apart from a few broken windows, the workers canteen was untouched. On the March 18th 617 Sq bombed the Explosives Works at Bergerac, when ‘Bunny’ Clayton tried something new. Just prior to releasing his 12,000lb ‘Blockbuster’, he dropped a standard 1,000 lb bomb. The 1,000 lb bomb exploded and detonated the ‘Blockbuster’ in flight, this 12,000 lb ‘air burst’ detonated the main explosives store with spectacular results. This new tactic was added to 617’s S.O.P. After each successful raid, Cheshire would send a brief damage report back to No 5 Group, results were becoming so monotonous he started sending a brief ,four word message that became an unofficial catch phrase for No 617 Squadron…..” In accordance with tradition”. Successful raids continued along with some more problems with weather forecasts. At the end of March 617 Sq was split into three flights from the previous two. Shannon and McCarthy were promoted to Squadron Leader and along with Munro became the Flight Leaders. Although Cheshire’s low level marking theory had now been proved, he had felt for some time that the Lancaster was not the best suited to the task. He felt a smaller more agile aircraft would serve better. Cheshire went to see Cochrane and having got him to admit the low level marking was working and that 617 Sq was getting results, he asked for two or three Mosquitos. Cochrane gave it some thought and then ran it past AVM Harris, Harris was of the opinion “what 617 Sq wants, 617 Sq can have”. So on the 27th March 2 Mosquitos arrived to join the Squadron. The other advantage of the Mosquito was, it could fly ahead of the bombers and see what the weather was really like. Dams veteran Dave Shannon and his bomb aimer Len Sumpter went to RAF Warboys for conversion training to the Mosquito as the rest of Shannons crew had been posted out as tour expired. At the end of March, 6 new Lancasters arrived with a strange bulge on the underside, this was H2S radar. It could differentiate between land and water, though crude by today’s standards, it would allow crews to bomb blind through haze, smoke and heavy cloud. With these new additions, 617 Sq continued to fly more and more very successful missions with very few losses. In mid-April 617 Sq said goodbye to most of their remaining ‘Type 464 (P)’ Dambuster Lancs. Flown so infrequently they were becoming a problem to maintain. They were therefore sent to RAF Metheringham, ostensibly for storage, although they were frequently flown by No 106 Sq on fighter affiliation, cross country and general transport flights. On April 18th, 617 Sq lead a raid on the railway marshalling yards at Juvisy. They would carry out the initial marking and bombing and be followed in by a further 200 No 5 Group bombers. The ‘considerable’ amount of damage done was put down to 617 Squadrons excellent marking. Since the disastrous Dortmund – Ems Canal raid in 1943, all but one of 617 squadrons targets had been in France. This had allowed them to perfect their low level target marking methods and this was something ACM Harris was keen to employ against targets in Germany. In the third week of April 617 Sq was put on standby for a raid against Munich, Darmstadt or Brunswick. On the 22nd they were briefed for the very heavily defended Brunswick railway marshalling yards…..