Like Brian Loudon (AJ 17/24.8.00) I too was an avid reader of Simon Templar novels as a lad, but a little earlier - in the late '40s.
However, his memory is playing tricks if he recalls Sebastian Tombs as being one of the Saint's principle adversaries. This was in fact Simon Templar's alias as he was known by much of the criminal fraternity to be the Saint. In the early novels by Leslie Charteris, the Saint's main adversary was a mid-European nasty called Rayt (or Rait) Marius.
Martin James, Caterham, Surrey