One of the the flamethrower design styles to come out of experimentation late in World War One was the toroid type, with a donut-shaped fuel tank and a central spherical pressure bottle. The British continued development on this type of weapon between the wars, and used it in World War Two. While the early models used a hydrogen spark ignition system, this was replaced in 1942 by a cartridge flare system like the US and Japanese models.
The tank on this example is a fiberglass one, and very lightweight. This was introduced after World War Two, and this one is an experimental model.
Armament Research Services (ARES) is a specialist technical intelligence consultancy, offering expertise and analysis to a range of government and non-government entities in the arms and munitions field. For detailed photos of the guns in this video, don’t miss the ARES companion blog post.