The internationally focussed FTSE 100 gained 1.5pc, but underperformed its European peers, as exporters were pressured by a recovering pound.
The currency recouped from an overnight dip as Prime Minister Boris Johnson was expected to return to his office "shortly" after being hospitalised with persistent coronavirus symptoms on Sunday night.
Stock markets globally were on steadier grounds after last week's modest selloff as new infections and deaths slowed in Italy and Spain, while hard-hit New York reported on Sunday that deaths had fallen slightly from the day before.
"We're seeing slowing cases in certain sections of Europe and that's bringing a rush of buying into the market," said Keith Temperton, a sales trader at brokerage Tavira Securities.
"However, longer-term impacts of what's happening and what happened are going to put pressure on the markets."
Despite policymakers injecting trillions of dollars into the global economy, the FTSE 100 was down about 28pc from its January peak due to company warnings and dismal economic data.
A survey on Monday showed British consumer confidence recorded its biggest fall in more than 45 years, adding to a batch of weak business activity data last week.
However, the risk-on sentiment pushed investors to buy some of the worst-hit sectors such as travel and leisure , which has nearly halved in value so far this year as country-wide lockdowns hamper travel demand.
Cruise operator Carnival Plc, IAG owned British Airways, easyJet jumped between 6pc and 9pc.
Aero-engine maker Rolls-Royce rose 13pc after it secured an additional revolving credit facility, but said it was scrapping its targets and final dividend.
Insurer Legal & General Group surged 17pc, recovering sharply from last week's losses after it said it would pay 2019 dividend even after a European Union regulator said insurers and reinsurers should temporarily halt payouts.
Peers Prudential and Aviva rose about 7pc.
The domestically focused midcaps gained 3.4pc, with Ladbrokes and bwin owner GVC jumping 10.2pc as it halved its estimate for a monthly hit to profits from the coronavirus-driven shutdown in international sports.
Healthcare company Novacyt rose 7.2pc after its COVID-19 diagnostic test won French approval, making it available for immediate distribution in France.