My previous question was a bit long, which might be why no one has answered it yet.
The punch line was , in 2002 a taxpayer rolls a capital gain over on one third of a private house, as he used it as his home office. He notified HMRC that no part of the room was exclusively used as office, but it was so during working hours, so he got roll over relief. When he retired in 2010 he emptied the room of files, and it became part of his PPR. Question: Did a chargeable gain arise at that stage?
He was working through a limited company, to which he charged rent- with full disclosure in his SATR.