Thank you so much - I tried all sorts of search engines and whilst I think this name came up I never quite got the definitive answer I was looking for.
I googled again and came up with the Forbes list of billionaires. Apparently there are 691 of them but some are coy about their age. So here is the oldest few who did give their ages -
Perry Bass 90 1.0billion United States
John Kluge 90 11.0billion United States
Anacleto Angelini 91 2.9bn Chile
Hugo Mann 91 2.6bn Germany
Maersk Mc-Kinney Moller 91 5.3bn ,
Robert Rich Sr 91 2.0bn United States
Saleh Bin Abdul Aziz Al Rajhi 93 3.2bn Saudi Arabia
Walter Haefner 94
Thanks again DaisyMae, I did a bit of research with those names and looks like the Walter Haefner chap is still around and classed as the oldest - now I'll enter the comp! Cheers.