That means he tops the Sunday Times newspaper's Richest of the Rich list - coming in higher than Microsoft boss Bill Gates, the richest living person in the world, who is currently worth £53.1bn.
William of Warenne, Earl of Surrey, was rewarded for his bravery in the Norman conquest by his distant cousin William the Conqueror.
He was given lands and estates valued at more than £57bn in today's terms.
That means he tops the Sunday Times newspaper's Richest of the
Rich list - coming in higher than Microsoft boss Bill Gates, the richest living person
in the world, who is currently worth £53.1bn.
The top half of the list, showing the richest 200 people in Britain since 1066, is dominated by early and medieval figures.
Enormous rewards
Three of the top four on the list came to England with William the Conqueror.
It reveals the enormous rewards he handed out to his allies for the part they played in the 1066 invasion.
Great 19th century industrialists and landowners also appear high up in the list, which excludes reigning monarchs.
Only four women feature on the list - the richest being Eleanor of Aquitaine (1122-1204) who was worth £7.8bn, placing her equal 45th.
The Archbishop of Canterbury
Thomas Becket, amassed a fortune which would amount to £19.2bn today.
Becket, who was born in 1118 and became a close confidant of Henry II, comes
10th on the list.
Clerics feature prominently, with 18 making the final cut, including Cardinal Thomas Wolsey - equal 38th on £8.6bn and William the Conqueror's half-brother Odo of Bayeux, who finishes equal fourth with £43.2bn.
The Sunday Times calculated its figures by taking a person's peak wealth as a proportion of the net national income of their country at the time, and expressing it as a percentage of Britain's gross domestic product for 1999.
Only six entrants on the list are still alive. Virgin tycoon Sir Richard Branson, who came third in the original Sunday Times Rich List, comes just 168th with £2.4bn.
Philip Beresford, who compiled the list, said: "Probably, the most striking fact revealed by the Richest of the Rich list is just how few people made their fortunes since the industrial revolution, let alone since the Second World War.
"Indeed there are only 11 20th century entries in the list."