Mountjoy is the granddaddy of tech in Ireland. He sold banking software firm Euristix to Fore Systems in 1999 for €80m, wisely taking payment in shares. Less than a year later Fore was taken over and Mountjoy doubled his money as the shares rocketed.
He has invested in some of the most successful Irish technology companies of the last 20 years, including similarity systems and Trintech, both of which were sold. There have been other stakes in BrownBag films, Perlico, Corvil, Duolog, Tango and most recently in Clavis, which is worth €50m after a funding round. The Sandycove-based investor has also backed Peralto, the consultancy firm set up by fraudster Breifne O'Brien's former wife Fiona Nagle.