Yeah, nut splitter and it is made offset or bent to give clearance. I bought a 1954 Anglia years ago and one of these saved a lot of hacksawing and torching to get it apart!
Concur, although not for Anglias - I have yet to have that joy (though, if I iive forever, I wouldn't mind owning one, but after I've owned a Studebaker Loewy Coupe and/or Gran Turismo Hawk, Citroen 2CV, and Lloyd Alexander). It's one of those tools you need just sometimes, but REALLY need when you do. The sound of the nut splitting is very satisfying.
This open-side design is superior to the "wrap-around" design, for obvious reasons. The offset can be nice, or frustrating, depending on how you can reach the nut. If it is a K-D, they seem to run about $36 online, and the plunger is available (part No. 715-75 - no idea of price).