The FTSE 100 has broken through the 7000-point barrier for the first time in its history.
It was last at 7010.03, up 47.71 or 0.7% on the day.
Britain's blue-chip index has been rising in the last few months as Greece neared a deal with Europe on its bailout and signs that US interest rates are likely to remain close to record lows.
Hints from the US Federal Reserve earlier this week that a rate rise was still some months off, along with momentum created by George Osborne's budget, helped it close at a fresh record high of 6,962.32 yesterday, beating its previous peak hit on March 5.
Strong early gains on Wall Street provided a fresh impetus in afternoon trading.
The 7000 level has been seen as something of a psychological barrier, as it has been 17 years since the index moved past 6000.
The FTSE got to around 6750 in 1999 but pulled back as the dot-com bubble burst.
Given the length of time it has taken to reach this height, Tom Stevenson, investor director at Fidelity Personal Investing, said it no-one should be celebrating.
"When you consider that the growth of the UK market has progressively slowed since its launch in 1984," he said.
"While it took just three years to double the index between 1984 and 1987, it was nearly a decade for it to double again between 1987 and 1996.
"Even if the market races ahead from 7,000 to 8,000 it will have taken the best part of 20 years for it to double for a third time."
