KEN COSTA, the City veteran who runs the European investment banking arm of UBS, knows a thing or two about client service. While on holiday in South Africa, during the Oppenheimer family’s bid to take de Beers private, an out-of-breath Costa took a call from Sir Chips Keswick.

The surprised De Beers board director queried whether Costa was exercising. With suitable sang froid the UBS man replied that he was on the run from a rampaging rhino who had forced him and a companion to take refuge up a tree.

He says: “I believe in providing that type of service. If you go that extra mile then your client will want to continue working with you in the end — and in the beginning and middle as well. It is relationships with people that matter.”

Costa, himself a South African, highlights the transaction as one of the highlights of career spanning nearly 30 years in finance.

It was a momentous deal for the Oppenheimer family, who took De Beers private for £13 billion in a deal that Costa says “was a good one because it was a win-win situation”. The diamond house was unbundled from Anglo American and is now owned by a consortium controlled by the Oppenheimers. The diamond transaction contrasts with Costa’s most scarring experience — the battle between Tiny Rowland and Mohamed Al Fayed for House of Fraser and Harrods.

He says: “We advised House of Fraser through seven cliff-hanging proxy battles in the 1980s.” Under protest, Rowland, head of Lonrho, eventually sold his House of Fraser shares to Al Fayed, after a long battle with the British Government over Lonrho’s right to bid for the store group.

“It felt like a seven-year war. It is difficult to know who won and I often ask myself whether it was worth it. In the end, Fayed got the shares from Tiny, and I believe that Tiny was until his death filled with seller’s remorse. It is the most difficult of all remorses to overcome.”

Costa, trim and 54 years old, is, to his very core, an old-style merchant banker. He cut his teeth under the late Sir Siegmund Warburg. As head of SG Warburg, now part of UBS, Sir Siegmund was considered by some to be the pre-eminent City banker of the post-war generation.

Costa has just been appointed to a new postition, that of chairman of investment banking for Europe, Middle East and Africa. His brief is to expand the division profitably. The bank has already bolstered its European team by hiring Piero Novelli from American rival Merrill Lynch to head European mergers and acquisitions. Costa is to be helped by Alex Wilmot-Sitwell and Jeff McDermott, who have been newly recruited as co-heads of European investment banking. Eighth in European M&A league tables, the house claims hopes of becoming the leading investment bank in Europe.

More than 30 years in Britain have all but erased Costa’s South African accent, leaving him with a modulated voice that comes in useful in the other major strand of his life — God.

As a warden and regular preacher at Holy Trinity church in Brompton, London, Costa is an evangelical Christian. He almost always carries a bible in his pocket and is chairman of Alpha International, an organisation aimed at introducing Christianity to non-believers.

The inevitable question — how does he manage to reconcile God and Mammon? “It is essential to have a value system that underpins every aspect of your life. Faith is a whole-of-life priority. I have found that in the Christian tradition, there is a seamless link between the work ethic and spirituality. This has pragmatic day-to-day consequences in dealing with anxiety, stress and the work/family life balance. A job well done, service to others, and caring for others.”

“I could not do the job I am doing without these foundations, without the moral foundations of faith. However difficult it may be, it helps to have very clear biblical views of right and wrong in a world where grey is where we often have to operate.”

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