Well my goodness what a shock.
Mark had said that he was having problems, at that time undiagnosed, but of course we always hope for the best.
He will be missed in this club for sure as he was so active and helpful, and I'm sure I speak for us all in offering you and your sister our heartfelt sympathy.
Mark was a bit of a pioneer with his build and was generous with help and advice to those of us following on.
Rest in peace Mark.