If you squint at it the right way, the UK's Black Arrow launch vehicle was steam-powered; it used HTP (85-98% hydrogen peroxide) as an oxidizer, which decomposes to oxygen plus superheated steam on its way into the engine (the oxygen was then combusted with RP-1 fuel). The steam contributes a fair amount of reaction mass:

https://en.wikipedia.org/wiki/Black_Arrow

... And the (one) satellite it successfully launched is still in orbit, nearly 50 years later.

You probably know this, but one can quite successfully skip the kerosene entirely and just use peroxide as a monopropellant with a silver catalyst.

Presumably Hughes's belief system demanded that all his silver exist in coin form, hoarded and buried in the backyard, or something.

117 seconds specific impulse [1] is miserable. It is possible [2] to reach orbit with that, but not efficiently.

1 - http://www.astronautix.com/h/h2o2.html

2 - https://space.stackexchange.com/a/8720

I believe that we (the UK) are the only nation to develop and test a orbit-capable launch vehicle and then scrap it?

This reminds me that there's a company claiming to be developing a steam-powered booster for orbital launches. Scott Manley did a video about them a while back [1]. Where this stands on the spectrum between a scam and a real thing remains to be seen, but they did seem to be convincing enough to get some investments and build a test rig.

[1] https://www.youtube.com/watch?v=qT9HBkWGg7s

The major distinguishing factors between a scam and an also ran in my opinion are that for something to be a scam the people running it have to be aware that it will not work and that they have not ignored any expert advice telling them that it will not work in sufficiently clear terms that they can't claim that it is just naysaying.

Plenty of people that relieved investors from their funds were unaware that what they were building was a scam.

Plenty of people working for companies that built stuff that didn't work were not aware of the fact that it could not work until they themselves established that.

Plenty of successes where there were people saying 'this can't possibly work' right up until the time that it did, in fact, work.

Theranos, Moller sky car, Ubeam (now renamed to SonicEnergy in an attempt to leave their past behind them) -> clearly scams.

This particular steam powered rocket is not a scam in the sense that it did not attempt to pass the risk or the eventual results onto others. It is merely very stupid, and it should serve as an object lesson in that if you are trying to do something in your backyard that normally has budgets in the 10's to 100's of millions that you are likely not going to succeed. Finally, it should teach people that your tests of vehicles of any kind that go up should be done unmanned as long as possible.