By Matt Scuffham and Chris Vellacott
LONDON (Reuters) - Royal Bank of Scotland
Stevenson was co-head of investment banking for Europe, the Middle East and Africa at Credit Suisse and has never been a finance director before. His other challenge at RBS will be to prepare it for a stock market return after depending on state handouts.
RBS, once a small Scottish retail bank, briefly became the world's biggest bank by assets following aggressive expansion before its collapse led to a 45.8 billion pound ($76 billion) government rescue, leaving taxpayers with an 81 percent stake.
Stevenson was on the team of Credit Suisse that advised the British government on its bailouts of RBS and Lloyds
That, said Bernstein Research analyst Chiran Barua "will give him a head start as to the idiosyncrasies of the RBS balance sheet and relation to its principal shareholder".
But one of RBS's institutional investors said he had doubts about Stephenson's suitability for the post.
"Intuitively a non-accountant investment banker does not sit quite right in that role," the investor told Reuters on Friday.
Stevenson will take up the role on May 19, filling the post vacated by Nathan Bostock - who quit RBS last year to join rival Santander
He will work with fellow New Zealander Ross McEwan, who became chief executive of RBS last October and Rory Cullinan, who heads up a division tasked with selling non-core assets such as RBS's U.S. retail business Citizens.
Ex-colleagues of Stevenson described him as a "no-nonsense" character, like McEwan, with an eye for detail and an appetite for hard work. He is also said to be unafraid to convey bad news and prepared to confront the reality of difficult situations.
Stephenson will need to maintain strong relationships with officials at UK Financial Investments (UKFI), which manages the government's stake in RBS, and Britain's Finance Ministry.
He will be able to build on an existing relationship with UKFI Chief Executive James Leigh-Pemberton, a former Credit Suisse colleague, who will have approved his appointment.
RBS is still three to five years away from being privatized, according to banking and political sources, in contrast to state-backed rival Lloyds Banking Group
McEwan is battling to revive the fortunes of RBS, which has been plagued by past misconduct issues, and has pledged to turn into the "best bank in the UK" rather than the biggest in the world. He took over from Stephen Hester, who had already overseen a massive restructuring and shed 900 billion pounds of assets from the bank's balance sheet.
In an internal memo seen by Reuters, Credit Suisse said it had appointed Alejandro Przygoda head of the global financial institutions group (FIG) at its investment bank, to replace Stevenson. Przygoda was previously co-head of global FIG alongside Stevenson.
Switzerland's second-biggest bank has also appointed Mark Echlin as co-head of its investment bank in Europe. He takes on the position alongside his current role as co-head of Credit Suisse's global industrials group.
Shares in RBS were down 0.2 percent to 316.3 pence at 1040GMT, meaning taxpayers are currently sitting on a loss of over 17 billion pounds following the government bailout. Shares in Credit Suisse were up 0.2 percent. ($1 = 0.6029 British Pounds)
(Editing by Sophie Walker)