Britain sells $20 bln book of Northern Rock loans to Cerberus

* Milestone in "clearing up mess" after crisis -Osborne

* "Granite" biggest loan portfolio ever sold in Europe

* Cements Cerberus as biggest buyer of European loans (Adds comments from CEO, details on Cerberus, background)

By Sarah Young and Steve Slater

LONDON, Nov 13 (Reuters) - Britain has sold 13 billion pounds ($19.8 billion) of loans once held by former mortgage lender Northern Rock to U.S. private equity firm Cerberus , marking the biggest ever sale of a book of loans in Europe.

Northern Rock, which was nationalised after nearly collapsing in 2007, came to symbolise the financial crisis in Britain and the sale of the 125,000 loans represents the latest stage of the British government's push to sell assets to help to pay down the national debt.

"Today marks another major milestone in clearing up the mess left by the financial crisis," finance minister George Osborne said.

The loans were sold for 280 million pounds ($426 million) more than their book value, recouping money for taxpayers.

Osborne is aiming to raise more than 30 billion pounds over 2015-16 by selling off publicly owned assets, and he said proceeds have now reached over 24 billion pounds since April 1.

In the past few months, the British government has sold more of its shares in Lloyds Banking Group and started to sell off part of its stake in Royal Bank of Scotland.

Cerberus will sell 3.3 billion pounds of the loans, or a quarter, to TSB, the British bank that was bought this year by Spain's Sabadell.

CERBERUS SNAPPING UP EUROPEAN LOANS

The sale of the Northern Rock portfolio, dubbed "Granite", cements Cerberus' position as the biggest buyer of loans that are no longer wanted by European banks which are shrinking in the wake of the financial crisis.

The New York based firm, named after the mythical three-headed dog that guards the gates of Hades, has bought more than 27 billion euros of European loans in the last three years.

In the first nine months of this year, it bought eight loan portfolios in Europe with a combined face value of 7.7 billion euros ($8.29 billion), more than any other firm, according to real estate brokers Cushman and Wakefield.

Most of the loans bought in recent years have been at knock-down prices, but the premium paid for the Granite portfolio was because most of the loans are being repaid and there was stiff competition for the assets.

UK Asset Resolution (NRAM), the body that is running down the Northern Rock loans, said 96 percent of Granite's customers were up to date with payments and the portfolio was spread across Britain with an average mortgage of 100,000 pounds. The portfolio also included unsecured loans sold by Northern Rock called 'Together' loans, which were tied to mortgages.

Richard Banks, chief executive of NRAM, said there were six bidders in the second round of the auction.

Sources have said they included offers from groups including JPMorgan and Blackstone.

The funding for Cerberus - a key part of such a hefty deal - has come from Bank of America, Credit Suisse, Morgan Stanley, Lloyds Banking Group and Natixis , people familiar with the matter said.

Morgan Stanley advised Cerberus and arranged its financing, while Credit Suisse advised UKAR.

The loans in the Granite portfolio will continue to be serviced by NRAM's mortgage servicing unit, although that business is up for sale and is expected to be sold in the next six months.

UKAR still holds about 42 billion pounds of former loans from Northern Rock and Bradford & Bingley, which was also nationalised. CEO Banks said there were no more major loan portfolio sales in the pipeline, but more could be done to speed up the repayment of UKAR's loan from the government.

"We are constantly on the lookout for ways of segmenting the portfolio and selling further tranches.

"There's nothing on the stocks at the moment, but it (Granite sale) does suggest that we can sell other assets and possibly do better than our expectation of paying the government debt by 2025," Banks said.

($1 = 0.6572 pounds) ($1 = 0.9284 euros) (Editing by William Schomberg and Jane Merriman)