The Hungarian-American financier George Soros made a profit of almost $1 billion during last month's devaluation of the British pound by betting heavily that the currency would collapse despite Government assurances to the contrary.

In an interview reported today in the Times of London, Mr. Soros said he had borrowed heavily to take his stand against the pound because he was confident the German Bundesbank wanted devaluations in Britain and Italy, but not in France.

In the weeks leading up to Sept. 16, known as Black Wednesday in Britain, Mr. Soros sold pounds, betting $10 billion that Prime Minister John Major would fail to keep the currency above its floor in Europe's Exchange Rate Mechanism.

He won, and Mr. Major lost. The onslaught by currency speculators forced Mr. Major to pull the pound out of the European Community's system for regulating the value of the community's national currencies. The pound was subsequently devalued by 12 percent.