This has quite a long heritage, with Reaction Engines Limited being co-founded by one of the designers of HOTOL[0], which was a similar design for an air-breath

This has quite a long heritage, with Reaction Engines Limited being co-founded by one of the designers of HOTOL[0], which was a similar design for an air-breathing rocket engine which got a lot of press in the UK in the 1980s. [0] https://en.wikipedia.org/wiki/HOTOL https://en.wikipedia.org/wiki/HOTOL