Judging by the Flight article Herbert Smith had an interesting career, retired rather early from aviation, but never got back into UK aviation.
There is clearly some dispute about who designed which Sopwith aircraft, but Herbert Smith gets a lot of credit, particularly for the later ones (Sopwith Cuckoo?). So he was a designer of considerable skill and reputation
http://www.flightglo...960 - 3097.html
As far as I can make out Tom Sopwith "phoenixed" "Sopwiths" in 1920 (that is he declared the original company bankrupt, paid off his creditors and then set up again with as "Hawkers Ltd"). AFAIK the change in company name was in tribute to Harry Hawker his chief test pilot, who had just died in a crash. But, Sopwith, Hawker and Sigrist were a very close group of friends and it appears that Herbert Smith was not part of the team that went on to form Hawkers. By the way, Sydney Camm joined Hawkers a few years later, so was not part of this series of events.
In the event, Herbert Smith joined another "band of brothers"; the British Naval mission to Japan that was sent to help prepare the IJN fight a "second front" war in the Pacific if the RN came to blows with the USN in the Atlantic.
However, the "unofficial" British Naval Aviation mission to Japan was a good idea that went rather wrong when the Brits decided that they preferred to be allied to the US rather than fight them!
It seems clear that at least some of the mission "went native" - Frederick J Rutland for one was caught spying for the Japanese, so it is not surprising that other members would be under suspicion.
What is clear is that the mission created the very effective Imperial Japanese Navies air arm - with a particular expertise in torpedo bombing!
However, a lot of good designers went to Japan at about that time - after all it was a time of retrenchment in Europe (Dr Voght of Bluhm and Voss springs to mind). The Flight article states that both Vickers and Hawkers tried to sign him on.
So, a good designer who never got back into the UK business and was under a certain amount of justifiable suspicion after his return from Japan.
And a cracking yarn as well!