A long, unobstructed bomb bay meant that the Lancaster could take the largest bombs used by the RAF, including the , and "blockbusters", loads often supplemented with smaller bombs or incendiaries. The "Lanc", as it was known colloquially, became one of the most heavily used of the Second World War night bombers, "delivering 608,612 long tons of bombs in 156,000 sorties". The versatility of the Lancaster was such that it was chosen to equip 617 Squadron and was modified to carry the Upkeep "bouncing bomb" designed by Barnes Wallis for Operation Chastise, the attack on German Ruhr valley dams. Although the Lancaster was primarily a night bomber, it excelled in many other roles, including daylight precision bombing, for which some Lancasters were adapted to carry the Tallboy and then the Grand Slam earthquake bombs (also designed by Wallis). This was the largest payload of any bomber in the war.