mick
I don't think there is any reason to suppose he did.
The first VDW letter was printed in the SCHB of 02/02/78 (item 2 of "The Golden Years..."), and the first G Hall letter a fortnight later, as a response (item 4). Then VDW's letter re staking plans (item 7) and the first substantial VDW letter in the 06/04/78 SCHB, the Erin one, (item 8).
Then a second one, including the "29 from 32" claim, in the 01/06/78 SCHB (item 13).
"The Golden Years ..." includes no letters in the next few months in response to that claim, though there might have been some that Mr Peach did not include and maybe in the Gummy material there is a post that will show there was. My bet, though, is that there were none and that frustrated VDW.
Hence not another VDW letter but an apparent third-party endorsement of the potential of "his system." (Letter from Hall in the 11/01/79 SCHB, (item 14). That was, we can now deduce, to try to stimulate discussion and designed so that VDW could reply (SCHB of 08/03/79, item 15).
This time VDW got the attention he was seeking with, we assume, replies from the likes of JP Hollis, A Duncan and F Chester and the long series of letters and replies got under way.
I can't see any reason why Mr Peach would have suspected Hall and VDW were one and the same then, and subject to checking I think there were no more letters from Hall as Hall. He had achieved his intention, becoming a focus of interest in the SCHB.
Why did he want that, given as far as I know he never tried to capitalise on it, for example by advertising tips or methods for sale, as one of his followers, Jock Bingham, did later? The most likely explanation, I think, is that he was interested in horse racing, had some genuinely interesting things to say and wanted to an extent to step out of the anonymity of an everyday sort of life in a respectable but perfectly ordinary job, living in a respectable but perfectly ordinary home in Market Harborough. Given his interest in racing, gaining some attention though the letter pages of the SCHB was his way of doing it. And given that here we are, discussing him and his letters and articles forty plus years later, means that if that was his aim he succeeded beyond anything he could have imagined.
I've met several people over the years who have had seemingly ordinary lives and ordinary jobs, who got the most satisfaction from what they did outside their 9-5 work; in amateur dramatics, abridging books for the BBC and becoming the acknowledged expert in a tiny corner of philately. Plus I've no doubt there are countless folk who get through the week at work thinking mostly about the cricket, football, golf or whatever they are looking forward to at the weekend. Come to that, it is why I am currently halfway through the seventh book in in a series about the fictional lives of a couple of secondary school teachers, maybe hoping that one day Steven Spielberg's office will get in touch to buy the film rights!
I can def feel my ears burning. 
