By Victoria Howley and Daisy Ku

LONDON (Reuters) - UBS AG has taken key roles on two landmark deals to shore up British banks -- landing the Swiss bank a welcome boost in fees and prestige on the same day it shocked the market with worse-than-expected results.

UBS is working alongside Bank of America Merrill Lynch to raise 13.5 billion pounds for Lloyds Banking Group in the world's largest rights issue.

It is also working with Morgan Stanley to advise Royal Bank of Scotland Plc on its participation in the UK government's Asset Protection Scheme (APS).

UBS's advisory team is led by Alex Wilmot-Sitwell, co-chief executive of the investment bank, and Chris Fox, a managing director in the bank's London financial institutions group.

Lloyds is paying 500 million pounds in fees and expenses, of which 190 million pounds will go to the six banks underwriting the rights issue -- UBS and Merrill alongside Citi, Goldman Sachs, HSBC and JPMorgan Cazenove.

As joint sponsors and global co-ordinators, UBS and Merrill are likely to earn more than the other four, implying payouts of more than 32 million pounds each.

Another 143.7 million pounds will be paid by Lloyds to the UK Treasury to reward it for taking up its entitlement, while 170 million will be spent on debt instruments and administrative costs.

The banks' fees equate to 2.25 per cent, plus a discretionary fee of 0.2 percent -- below the 2.75 percent base fee paid by HSBC Holdings Plc when it raised 12.9 billion pounds in April.

Wilmot-Sitwell, educated at the elite Eton College and at Bristol University in the west of England, is the son of former SG Warburg chairman Peter Wilmot-Sitwell. He was named co-CEO of UBS investment bank in April, making him one of London's most senior bankers.

Warburg was bought by Swiss Bank Corp in 1995 and subsequently became part of the merged UBS.

Wilmot-Sitwell joined UBS in 1996 as head of corporate finance in South Africa, moving to London two years later to head up the UK investment banking operation. This year he helped miner Anglo American Plc rebuff a merger approach from rival Xstrata Plc.

Fox, a Cambridge university graduate, joined UBS in 1993 as a qualified accountant. He previously led the bank's work with central and eastern European banks and now focuses on Middle Eastern and North African clients and on government work.

Earlier on Tuesday, higher-than-expected accounting charges pushed UBS into its fourth straight quarterly loss and its shares were hit by hefty withdrawals from its key wealth and asset management businesses.

RBS has not arranged a rights issue but says it is an option. A source familiar with the matter has said previously it could raise 3 to 4 billion pounds and bankers say it could pay fees of up to 3 percent -- or as much as 120 million pounds.

Credit Suisse AG and Deutsche Bank AG are advising the UK Treasury.

(Additional reporting by Quentin Webb; Editing by David Holmes)