Sir Leonard Blavatnik has topped the latest Sunday Times Rich List, having seen his fortune swell to £23bn.
The Ukranian-born oil and media magnate, who also owns Warner Music, saw his wealth surge by £7.2bn during the year.
He took the title from Sir James Dyson, whose wealth rose by only £100m to £16.3bn, leaving him in fourth place.
There are now a record 171 billionaires in UK, with their wealth rising 21.7% during the pandemic to £597.2bn.
Mr Blavatnik's fortune was boosted by the proceeds of a £1.37bn stake in Warner, which he received when it listed on the stock market in the US last year.
"The fact many of the super-rich grew so much wealthier at a time when thousands of us have buried loved ones and millions of us worried for our livelihoods makes this a very unsettling boom," said Robert Watts, compiler of the annual index of the country's wealthiest residents.
"The global pandemic created lucrative opportunities for many online retailers, social networking apps and computer games tycoons."
Property investor brothers David and Simon Reuben were in second place after their fortune grew by £5.46bn to £21.46bn.
Sri and Gopi Hinduja, who run the Mumbai-based conglomerate Hinduja Group, took third spot after their wealth rose by £1bn.
Steel magnate Lakshmi Mittal, in fifth place, saw the biggest rise in wealth of any billionaire in the past 12 months, with gains of around £7.9bn, largely based on the rise in value of his ArcelorMittal steel-making business.
Chelsea owner Roman Abramovich was in eighth position after his fortune rose by £1.9bn to £12.1bn.
The total of 171 billionaires in the latest Rich List is higher than the previous record of 151 set in 2019.
The study found the richest 250 people in the UK this year are worth £658.1bn, up from £565.7bn last year, a rise of 16.3%.
Soaring tech values
There are also more entrepreneurs behind unicorns - start-up businesses with a valuation higher than $1bn - to be found in the Rich List than before.
They include Farfetch, the luxury online fashion retailer, whose founder Jose Neves is a new entry at 82 in this year's Rich List with a £2bn fortune.
Alex Chesterman, founder of online car dealing service Cazoo makes his first appearance at 215th with an estimated worth of £750m.
"The valuations of many rich listers' companies have soared over the past year - especially the pack of tech businesses known as unicorns," said Mr Watts.
"I worry about the strength of the foundations. No-one wants to see a re-run of the dotcom boom-and-bust of 20 years ago."
Top 10 Billionaires
These are the 10 richest people in the country according to the Sunday Times Rich List:
1, Sir Leonard Blavatnik - £23bn (oil and media)
2, David and Simon Reuben - £21.46bn (property and internet)
3, Sri and Gopi Hinduja and family - £17bn (industry and finance)
4, Sir James Dyson and family - £16.3bn (household goods and technology)
5, Lakshmi Mittal and family - £14.68bn (steel)
6, Alisher Usmanov - £13.4bn (mining and investment)
7, Kirsten and Jorn Rausing - £13bn (inheritance and investment)
8, Roman Abramovich - £12.1bn (oil and industry)
9, Charlene de Carvalho-Heineken and Michel de Carvalho - £12.01bn (inheritance, brewing and banking)
10, Guy, George, Alannah and Galen Weston and family - £11bn (retailing)