After gaining as much as 1.2%, the commodity-heavy FTSE 100 closed up 0.3%, with BP Plc and Royal Dutch Shell Plc among the biggest boosts.
Oil prices rose on an improvement in Chinese factory data, hopes for more coronavirus-related stimulus from the United States, and as Saudi Aramco forecast rising energy demand.
Material stocks also gained 4.6%, while defensive plays such as healthcare stocks led losses.
The mid-cap FTSE 250 closed at a seven-week high with shares of shipping services provider Clarkson jumping 12.1% as it resumed dividend after a first-half profit rise.
Focus was on U.S. stimulus after President Donald Trump signed executive orders on Saturday partly restoring enhanced unemployment payments.
The FTSE 100 has rallied about 24% since its March low but has unperformed both European and U.S. benchmarks as a persistent rise in COVID-19 cases threatens a nascent business recovery.
Britain on Sunday reported its highest daily rise in new infections since late June. On Monday it recorded a slightly lesser 816 new cases.
A clutch of data will be eyed this week, including the unemployment rate and June gross domestic product figures.
"By July, we think that around 4 million people had already left the government's job furlough scheme and 5 million remained on the scheme," said Ruth Gregory, Capital Economics' senior UK economist.
"That fall is faster than we had expected but does not change our forecast that the ILO unemployment rate will reach a peak of around 7% by mid-2021."
Fashion retailer Superdry jumped 18.7% to a one-month high after agreeing a new 70 million pound lending facility to get it through the coronavirus crisis.
By Sagarika Jaisinghani and Susan Mathew