The FTSE 100 Index defied expectations for a lacklustre start by opening more than 20 points higher.
Further gains by Unilever and a strong session for miners meant the Footsie reached 6171.4 in the first hour of trading, a gain of 23.3 points.
Market watchers had forecast a flat opening as investors remained on the sidelines ahead of economic news on both sides of the Atlantic later in the week.
The rise of 2% for Unilever - up 25p to 1391p - came after last Thursday's results from the foods giant brought evidence of improved trading in Europe.
Among the miners, Xstrata lifted 34p to 2339p and Vedanta Resources cheered 25p to 1490p.
Two firms due to report figures on Tuesday - Yell and Associated British Foods - were in positive territory as investors looked for good news. The pair were ahead by 13p and 12p at 631.5p and 847p respectively.
Marks & Spencer will also present interims on Tuesday, but saw its share price slip 2.5p to 654p.
In the gaming sector, shares in 888 Holdings jumped 8% or 8.5p to 119p after it emerged that Ladbrokes was in talks over a possible takeover.
The high street bookmaking business was 2p higher at 412p, while another potential merger partner for 888 - PartyGaming - stood 0.75p higher at 28.25p.
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