The death has occurred of Denis (Dano) O'Brien, father of telecoms and media entrepreneur Denis O'Brien jnr.

A Cork native, Mr O’Brien (85) was a long-time resident of Dublin’s Ballsbridge and a father of four. In his youth he was a champion high diver and reportedly dived off the cliffs in Acapulco, Mexico.

He founded Plus Vital in the 1970s, a company involved in the global manufacture and distribution of horse-care products. His son has credited his father’s involvement in business as an inspiration in his own career.

Mr O’Brien snr was a founding director of Esat Telecom, the company established by his son and which, by way of its involvement in Esat Digifone and the winning of the State’s second mobile phone licence, created the springboard for Mr O’Brien jnr’s entry into the ranks of the super-wealthy.

When the Esat Group was sold to BT in 2000, Mr O’Brien snr’s share of the price paid was reported to be £3 million (€3.8 million).

Mr O’Brien snr joined the board of his son’s radio business, Communicorp, in January 1990 and was on the board up to 2005.

When the Moriarty tribunal was conducting hearings into the second mobile phone licence competition, Mr O'Brien snr frequently attended, sitting in the public gallery. In 2001 he went on RTÉ's Liveline to complain about how his son was being treated by the tribunal.

Mr O’Brien is survived by his wife, Iris, and his children, Joanne, Abigail, Denis and Kerry. Requiem Mass is at noon tomorrow in the Church of the Sacred Heart, Donnybrook, Dublin 4.