>>717794607
Dario Casali, John Guthrie, Steve Bond, and Tom Leonard were the Ravenholm/City 17/Canals cabal during the development of Half-Life 2.
After Half-Life 2 and the Episodes, Leonard ended up doing a lot of work with Mike Booth on the L4D and L4D2 AI Director and then on Source 2 engine development, but ultimately Leonard was caught on the losing end of the Valve internal politics infighting over company direction in the 2013 era when Michael Abrahs was pushing to turn Valve into a VR company. He wasn't the only one, either. For other big names at Valve that were caught in the 2013 purge, see:
https://www.pcgamer.com/valve-layoff-hardware-mobile/
Tom Leonard still appeared in the Half-Life 2 20th Anniversary Documentary so I'm guessing personal feelings have gotten over it in the intervening years, but Valve supposedly has a policy of never re-hiring anybody who was fired, so he's never coming back unfortunately.