Infact a mixture of butane and propane. I was looking for a small stove that will fit on the bike somewhere and not cost a fortune. There are plenty of liquid fuel stoves available but they all cost good money and unless you are going out of Europe and/or need to make a cup of tea at the top of a mountain or in the extreme cold they are possibly a bit over the top. I the end I went for a folding gas stove from Vengo that folds into a small plastic box and takes standard screw top gas canisters.
I gave it a quick test this evening to cook sausages, that’s the sort of testing I like! It is a pretty lively stove with a high, very high, and ultra high settings, sounding much like a jet taking off. I did get it low enough to be able to gently cook on and all worked pretty well. Tom and Jack confirmed the sausages had passed their testing!