The estimated value of goods stolen in the Hatton Garden raid has risen to around £25m, a court heard.

It had originally been thought that some £14m worth of goods had been snatched during the robbery – most of it still missing.

It is thought the prosecution is seeking up to £25m from five of the men at the heart of the conspiracy.

Ringleaders John “Kenny” Collins, 76, of Islington, north London; Daniel Jones, 62, of Enfield, north London; Terry Perkins, 68, of Enfield; and the group's oldest member, Brian Reader, 78, of Dartford, Kent, pleaded guilty to conspiracy to commit burglary.

Collins, Jones and Perkins were each given a seven-year prison term for their involvement in the burglary over the 2015 Easter bank holiday weekend.

The gang ransacked 73 boxes at Hatton Garden Safety Deposit in London's jewellery quarter after using a drill to bore a hole into the vault wall.

William Lincoln, 60, of Bethnal Green, east London, was found guilty of the same offence and one count of conspiracy to conceal, convert or transfer criminal property.

Lincoln was also given a seven-year sentence.

Referring to the amount being sought in confiscation proceedings, Denis Barry, representing Jones at Woolwich Crown Court, said: “The Crown say £25m between five.”

The court heard that a full confiscation hearing is expected to last around six weeks, and a date was set for 15 January 2018, with a deadline of 30 April that year.

Philip Evans QC, prosecuting, said: “This is an exceptional case which warrants an extension.”

If members of the gang do not pay back what the judge rules they gained from the crime, they could face up to a maximum of 14 years of jail time being added to their sentences, without parole.

Tom Wainwright, for Reader, asked for a QC to be appointed to his client's case, stating they would have the required skill to deal with proceedings of this length and Reader's health.

He said: “The case is made more complex because Mr Reader is not in good health.

“He is likely to be in worse health come December or January.”

In June 2016 – after the trial – a woman came forward reportedly alleging that she had lost £7m worth of gold in the raid.

At the end of the trial, two-thirds of the proceeds of the burglary remained unaccounted for. During the case, the court heard that 44 of the 73 boxes were actively used by 40 tenants at the time.

Although some of the goods – around £4m worth – were recovered, detectives were left with “thousands of items of jewellery”, including hundreds of gold chains and rings and many paper packages used in the jewellery trade – known as “Brifkas” – containing individual precious stones.

The confiscation hearing, under the Proceeds of Crime Act, will determine how each of the defendants benefited from the raid.

Also convicted were Carl Wood, 59, of Cheshunt, Hertfordshire, who was found guilty of conspiracy to burgle and one count of and conspiracy to conceal, convert or transfer criminal property.

He was jailed for six years.

Plumber Hugh Doyle, 49, of Riverside Gardens, Enfield, north London, was found guilty of concealing, converting or transferring criminal property between 1 January and 19 May 2015.