He noted that the size of the stone leg seems disproportionately large, even for a statue the size of Alfred. 

The Roman section is made of a Cotswold limestone, a “Bath stone” from a block that would have been brought downstream on a barge type vessel on the Thames.

“It is very well carved, showing muscle definition, probably by a continental craftsman used to working native British stone,” Dr Hayward said. 

The upper half of the statue is Coade stone, which was attached to the Roman statue in a complex process. The research also rules out the Richard II theory as those statues were created in Reigate stone. 

Dr Chris Constable, Southwark’s borough archaeologist, said: “It’s really exciting to find out that there’s been a piece of Roman sculpture on display in London since at least 1831, the first evidence we have for King Alfred standing in Trinity Church Square. 

“There have been an enormous number of theories about it. It’s always been mentioned quite vaguely as the oldest statue in London – and now it probably is. At least part of it is 1,000 years older than we thought.”