Asia-focused financial stocks, gaining on upbeat data from China, and a weaker sterling thrust London's main index to levels not seen since October, while mid-cap retailer JD Sports hit a record high after a forecast-beating profit.
The FTSE 100 added 0.4 percent after hitting its highest since Oct. 4 as a dip in pound boosted blue-chip exporter stocks.
The more domestically-focused midcap index built on last week's momentum, when the European Union agreed a second delay to Brexit, and clung to its six-month high with a 0.6 percent rise.
Both followed gains in Asia after data showed that new home prices in China grew slightly faster in March after a slow-down the previous month, kindling hopes that Beijing's stimulus measures were having an impact.
Hopes that the Sino-U.S. trade dispute would soon be resolved also gave some support as investors waited for growth figures from the world's top metals consumer.
That pushed up Asia-exposed financial heavyweights HSBC and Prudential between 1.1 percent and 2.7 percent. Miners also firmed after steep losses in the last session.
"Hopes towards what the Chinese GDP numbers might say tomorrow (Wednesday) combined with a more positive interpretation from the IMF's Spring meeting over the weekend have helped perceptions towards growth-sensitive sectors like miners and banks," said Raymond James analyst Chris Bailey.
The index did trim gains slightly after data showed British workers' pay grew at its joint fastest pace in over a decade, driven by further job creation, adding to suggestions that Brexit uncertainty is prompting firms to hire workers rather than make longer-term investment in equipment.
But a dip in pound came to the aid of FTSE 100, whose constituents book over two-thirds of its profits in U.S. dollars.
Sterling slipped after the Guardian newspaper reported that talks between Prime Minister Theresa May and the opposition Labour Party regarding Britain's exit from the European Union had stalled. The Labour Party denied the report.
Among a handful of blue-chip losers was Sainsbury's which gave up 1.2 percent after brokerage Bernstein cut its price target and said it could not consider the stock as a "buy-case".
On the FTSE 250, JD Sports was at an all-time high with a 8.4 percent leap as millennials' fondness for athleisure wear helped the company defy Britain's retail gloom and beat full-year earnings expectations.
Emerging market-focused asset manager Ashmore advanced 6.3 percent after reporting a double-digit jump in assets under management and retailer Card Factory jumped 10 percent following its annual results.
Capping gains on the index was Galliford Try, which plunged to a near 7-year low and ended the day with a 20.5 percent slump after saying it was undertaking a strategic review of its construction business that would lead to a fall in annual profit.
Hays shed 2.6 percent as the recruitment firm's organic growth in Australia and Germany slowed in the third quarter.