Barnes Wallis

Royal Airforce requested in 1942 a large conventional bomb they could use against particular u-boat bunkers, tunnels and bridges. The solution was "Tallboy" a 5.5 tonnes bomb with a length of 6.35 meters and a diameter of 95 cm. The bomb was designed by Barnes Wallis and was ready by summer 1944.

When the bomb was thrown from 6,000 meters altitude, it could penetrate up to four meters of reinforced concrete.

If the bomb was thrown against a soft target such as a railway hub, it would make a bomb crater 30 x 30 meters and 15 meters deep.

The bomb was filled with 2400 kg. of the explosive torpex that were 50% more powerful than TNT.

Concurrently with the development of Tallboy bomb was an even bigger bomb, the "Grand Slam" developed. It was 7.7 meters long and had a weight of 10 tonnes.

"Grand Slam" was used twice against u-boat bunkers. First time in March 1945 against the Valentin bunker in Bremen, where two bombs penetrated the 7.5 meter thick ceiling above the still unfinished bunker.

The second time was in April 1945 against the u-boat bunkers in Hamburg.