The growth of the Sega part of Mastertronic's business, the partial acquisition by Virgin in 1987, full control in 1988 and the sale of the whole of Virgin Mastertronic, except the core games business, to Sega in 1992 is covered in the history section. Until I stumbled on this piece I had no idea how much Sega paid for us.
The "Robert" mentioned below is Robert Devereux, head of the Video division into which Virgin Mastertronic was placed. For the sake of the record, I never met him, or Branson.
Pity about the misspelling of Frank's name, and arguably Mastertronic began in 1984 not 1983, but as far as I can tell the rest of the extract is accurate. It has been lifted from "Losing My Virginity" by Richard Branson and this extract was on the Google Books website and is therefore, effectively, in the public domain.