Before working on Doctor Who Tosh was briefly script editor on the series Compact, and had helped to develop the show that eventually became Coronation Street.
On Tosh's final story, The Massacre of St Bartholomew's Eve by John Lucarotti, Tosh performed a substantial rewrite of the scripts, both to align them with historical accuracy and also to accommodate William Hartnell's dual role as both the Doctor and the Abbot of Amboise.
[3] On the final episode the story editor's credit was given over to his successor Gerry Davis and Tosh was co-credited.
He was Head Custodian of Sherborne Old Castle, Dorset and St Mawes in Cornwall.
In 2013 he appeared as an extra in An Adventure in Space and Time, a drama about the making of the William Hartnell era of Doctor Who, made to commemorate the show's 50th anniversary.