Powder Boats This boat was one of a number built between 1850 and 1936. They were used to convey Gunpowder and later Cordite around the waterways of the Royal Gunpowder Mills. This particular boat, No. 20, was built in 1920 and it is now unique and is registered on the Small Boat Register as No. 2100. This wooden 'Green Hut' was originally erected here c.1940 as an additional Laboratory (L185) and has been substantially renovated to become 'home' to the last (and unique) example of the Powder Boats used to transport explosives materials around the network of narrow canals on the Royal Gunpowder Mills site. Both the Green Hut and the Powder Boat have been restored by dedicated members of the RGM Friends Association.