Heavy-weight financial stocks made a late charge on the London market as investors remained "upbeat" ahead of Thursday's vote on Britain's membership of the EU.
A lacklustre day's trading gave way to a rally at the end of the session, briefly pushing the market through the 6300 barrier for the first time in three weeks.
The FTSE 100 Index ended 34.6 points higher at 6261.2, as Hargreaves Lansdown and Old Mutual dominated the biggest risers, up 54p to 1381p and 5.6p to 193.4p respectively.
Analyst Tony Cross of Trustnet Direct said the market was clearly "upbeat" on the way it thinks the vote is heading.
"The FTSE-100 is marching its way higher and even though that brief test of territory above 6300 proved short-lived, there can be little doubting the way that sentiment has swung round - in the region of £100 billion has been added to London's blue chip equities since those lows last Thursday, and the market is pricing in less than a 25% chance of the Leave camp now winning."
Sterling was marginally higher against the dollar at 1.468 after touching its highest point since the start of the year on Tuesday. The pound was down 0.1% against the euro at 1.301.
The price of oil had swung back into positive territory after data from the American Petroleum Institute showed a larger than expected draw on stocks.
But data later in the session showed a smaller-than-expected weekly US inventory draw, causing Brent crude to slip 1.7% to 49.75 US dollars a barrel.
In stocks, easing Brexit concerns handed a boost to housebuilders, with Persimmon and Taylor Wimpey climbing 40p to 2086p and 2.6p to 188.2p respectively.
Primark-owner Associated British Foods was the biggest faller, down 3.4% or 99p to 2802p, after it was downgraded to equal weight from overweight by Morgan Stanley.
Away from the top tier, shares in department store chain Debenhams dropped more than 6% after it revealed falling sales amid "uncertain trading conditions".
The group posted a 1.6% fall in like-for-like sales for the 15 weeks to June 11 with currency movements stripped out, and warned that its profit margins would be lower than expected as it slashed prices to shift stock.
Debenhams said it had used "tactical" discounting after seeing weaker sales of womenswear since the new year, but added that it remained on track with an overall move to cut down on promotions and special offers.
Shares were down 4.6p to 69.7p.
Model railway maker Hornby slipped 2p to 30p after its boss promised "fundamental change" as annual losses ballooned to £13.5 million from £0.2 million in 2015.
Chief executive Steve Cooke said the company will raise £8 million through a share sale, reduce costs and renegotiate its loans as part of a wide-ranging turnaround plan following a strategic review.
The biggest risers on the FTSE 100 index were Hargreaves Lansdown up 54p to 1381p, Old Mutual up 5.6p to 193.4p, Provident Financial up 81p to 2846p, Standard Life up 9.3p to 340.7p.
The biggest fallers were Associated British Foods down 99p to 2802p, Antofagasta down 8p to 425p, Coca-Cola HBC down 24p to 1399p, Rangold Resources down 65p to 6400p.