Nigel Broackes, a self-effacing tycoon who restored the fading Ritz and rescued the sinking ship QE 2, today bought the ailing Beaverbrook newspapers for $23.5 million.

The deal will ultimately drive one of the mightiest press dynasties from Fleet Street. But it will also insure - for three years at least - the survival of the Daily and Sunday Express and the Evening Standard.

Broackes bought the three papers with his Trafalgar House Investments Ltd., a British conglomerate that owns shipping lines, hotels, construction companies and, above all, real estate. Its profits after taxes last year were $37 million.

Broackes, 42, the founder and boss of Trafalgar, is one of a handful of Britons who have prospered in hard times through property deals.

His Trafalgar concern has been an astonishing success with assets of $750 million. Six years ago, financial leaders thought Broackes had lost his grip when he paid 25 million pounds for the Cunard Line and the QE 2. But he turned both the steamship company and its most famous liner into profitmakers. Again last year, he paid $4.3 million for the splendid but unprofitable Ritz hotel. Broackes saw he could fill it with first-class passengers from his QE 2 and claims the hotel is already making money.

What he sees in the Beaverbrook papers is as much a mystery as some of his other ventures. They are losing at an estimated yearly rate of about $4.3 million. The literate, brightly edited Standard is highly respected. But its circulation of 425,000 makes it a loser in Fleet Street The Sunday Express, circulation nearly 6 million, can make money. But it is as little regarded as its stablemate, the Daily Express, with a fading circulation of about 2.4 million.

The Daily Express was once the pride and joy of the Canadian millionaire, Max Aitken. His devoted service to Troy politicians here won him a hereditary peerage and, as Beaverbrook, he was the great press lord for nearly 40 years.

Beaverbrook put an armored crusader in red ink alongside the paper's nameplate and campaigned tirelessly to preserve the British empire. At the height of the paper's strength, the Express sold 4.3 million copies a day and someone from its army of foreign correspondents could be found at every major world story. It was the most important popular newspaper in Britain, dearly loved by the great middle class.

But Lord Beaverbrook died in 1964 and his newspaper empire dwindled under his son. Sir Max Aitken declined to take his father's title and failed to find a new mission for his press. Now 67 and recovering from a stroke, he recently began seeking a buyer for the 58 per cent of the voting shares that he and his family foundation own.

Broackes had to beat out at least three competitors for his strange new prize. Vere Harmsworth, owner of the Daily Mail and the Evening News, wanted to buy in, probably to kill off his chief rivals. Sir James Goldsmith, the jet-set financier and new owner of Paris' L'Express, bought 40 per cent of the non-voting Beaverbrook shares and also tried to take over. Finally, Rupert Murdoch, the Australian who recently bought the New York Post, New York magazine and the Village Voice, made a bid.

Under the deal, Sir Max will stay on as president of the Beaverbrook group. The real chief will be Victor Matthews, Broackes' sidekick and deputy.

Tonight, Matthews talked about the Express, now shrunk to a tabloid, in words that would have warmed the nationalist heart of the old Beaver.

"Britain needs to know about the good things that are being done," Matthews said. "Achievements can be written about and perhaps merit more coverage than petty strikes."

Editors, he said, will have "complete freedom as long as they agree with the policy I have laid down." This, he said, means to "believe in Britain, look for the good things" and avoid pornography.

Does such a policy mean he would suppress a Watergate scandal in Britain?

"If it had happened here, it would have been a dilemma for me," he acknowledged.