[OJFord]

Had to dig through the archive a bit, but this one calls Fujitsu its 'IT partner':

https://www.computerweekly.com/news/252459274/Post-Office-co...

I don't know why it's not more prominent, Wikipedia 'Horizon (IT system)' doesn't say who created it either. Between 19th century and the second world war, the Royal Mail (General Post Office) employed engineers and researchers, established telephone service (British Telecom later span out), telegrams, and built Colussus, the computer that helped crack Enigma. But I imagine those days are over; I doubt Horizon was developed in-house.

[mannschott]

Colossus was used to crack Tunny (Lorenz cypher machine) used by German High Command, while the Bombe machines were used to attack Enigma.

[OJFord]

Thank you, you're right of course, I couldn't recall 'Tunny' and hoped I'd get away with 'helped' as general contributory effort in that line of work with 'Enigma' as something everyone's heard of. Probably should have said 'used at BP' or something instead though.

[eru]

Well, even earlier private entrepreneurs were running the London Penny Post (https://en.wikipedia.org/wiki/London_Penny_Post) before it got nationalized as a cash cow for the government (and divers other reasons).

[OJFord]

I meant that it was doing technologically advancing work around that time rather than that it was necessarily entrepreneurial.

I don't know if that was the case earlier, whether it involved itself with the R&D of better/faster road or railway carriages, for example.