Thousands of investors made millions of pounds by buying shares as the FTSE 100 Index fell 200 points and then watching it rebound sharply the day after.
The number of transactions broke a record during the day, hitting about 350,000 against an average in the last quarter of about 300,000, a London Stock Exchange spokesman said.
“In terms of the number of trades, it was the busiest day we have ever had,” he said.
Investors traded 4.75 billion shares compared to the recent daily average of about 3.1 billion.
Financial spreadbetting firm City Index reportedly said more than 8,000 retail investors dived into the market on Thursday, allowing the FTSE to recover more than 100 points by the close.
On Friday, the market ended the session at similar levels to those seen before Thursday morning.
Automatic trading systems used by institutional investors began dumping stock when shares fell sharply on news of the blasts, creating an opportunity for other investors.
However, City authorities reportedly considered closing the City down after hearing news of the blasts.
A committee of officials from the Treasury, the Bank of England and the Financial Services Authority, held urgent telephone talks to decide whether to suspend market trading after the attacks, according to weekend reports.
Members of the committee eventually took no action after deciding the attacks had not jeopardised market stability.
However, the blasts could cause more misery for beleaguered retailers, another report said.
Analysts expect visits to the capital’s stores to have slumped by up to 50% over the weekend.
Retailers in the capital could lose billions as a result of the tragedies, although it is predicted that tourism in the capital will return to normal in four to five months.