Israeli shipping billionaire Sammy Ofer wrote himself into the record books of philanthropy yesterday as he made what is believed to be the largest single donation to a UK cultural institution with a £20m gift to expand the world-renowned National Maritime Museum in Greenwich.

The bequest will help fund a major £35m development programme that includes the construction of a new wing to be opened in time for the museum’s 75th anniversary and London Olympics in 2012.

After yesterday’s signing ceremony at the museum, Mr Ofer, who closely guards his privacy, said: “I look forward to helping this hugely exciting project and believe it will be a great step forward for the museum.”

Museum staff were told of the donation and development plans last night, with a formal announcement expected this morning.

Prime Minister Gordon Brown offered his personal appreciation of the historic gift. He said: “Our maritime story is Britain’s national story. This generous donation by Mr Ofer will help ensure that current and future generations understand better the crucial role played by the sea in our history and the lives of those who depended upon it.

The museum’s development plans centre on the construction of a new Sammy Ofer Wing to the southwest of the current main building able to host major international exhibitions, as well as with new access to the museum’s huge archives, restaurant and shop, all opening onto Greenwich Park.

Mr Ofer, who is based in Monaco but has homes in London, Tel Aviv and elsewhere, heads a huge private family-owned shipping, industrial and finance group, including Tanker Pacific in Singapore and Zodiac Maritime Agencies in London, which now ranks as the largest operator of UK registered vessels.

Greenwich will again be the centre of attention today with a visit by French President Nicolas Sarkozy to the Royal Observatory as part of his state visit when he will present the Legion d ‘ Honor to Ellen MacArthur.