Nirav Modi has remained behind bars in judicial custody since his arrest in March. (FILE PHOTO)

The UK High Court on Tuesday began hearing fugitive diamond merchant Nirav Modi's appeal against a lower court's order to deny him bail as he fights his extradition from Britain to India in the nearly USD 2 billion Punjab National Bank (PNB) fraud and money laundering case.

Justice Ingrid Simler at the Royal Courts of Justice in London began hearing the arguments presented by Nirav Modi's legal team in an attempt to persuade the judge to overturn the Westminster Magistrates' Court ruling to deny bail during three previous attempts, for fear that the 48-year-old would fail to surrender.

"The reality is that he is not the cold-blooded hardened criminal as claimed by the government of India but a jewellery designer from a long line of diamond dealers, and regarded as being honest careful and reliable," said Clare Montgomery, Nirav Modi's barrister, as she opened the arguments in the hearing.

Judge Simler intervened to indicate that she has noted that Nirav Modi does possess the "means" to flee the UK and that factor must be a feature in a case involving "such sizeable funds".

She is expected to give her ruling in the matter later on Tuesday after hearing all the arguments presented by Nirav Modi's legal team and the UK Crown Prosecution Service (CPS), on behalf of the Indian government.

Nirav Modi has already been denied bail at three previous attempts at Westminster Magistrates' Court in London, as the judge ruled there was "substantial risk" that he would fail to surrender and deemed the bail security offered as insufficient.

Nirav Modi, who has remained behind bars in judicial custody since his arrest in March, had the automatic right to file an application in the higher court and did not require permission to appeal.

His legal team has described their client's experience at Wandsworth prison in south-west London as "damaging" and had offered stringent electronic tag and other conditions akin to house arrest at his posh Centrepoint apartment in the West End of London in an attempt to persuade the judge to grant bail.

At the first case management hearing in the case at Westminster Magistrates' Court last month, the issue of bail was not raised and Nirav Modi was further remanded in judicial custody until June 27, when he is scheduled to appear via videolink.

At the hearing on May 30, Judge Arbuthnot directed the Indian government to confirm which prison Nirav Modi is to be held in if he were to be extradited to India, setting a 14-day deadline for a confirmation of the prison plans in India.

Judge Arbuthnot, who ordered the extradition of liquor tycoon Vijay Mallya in December 2018, had sought a video of the exact cell at Arthur Road Jail in Mumbai in which the former Kingfisher Airlines boss is to be held. She therefore indicated that if Nirav Modi was to be lodged within the same premises, the court would most likely not have any objections.

The CPS has until July 11 to present an opening position statement laying out the prima facie case against Nirav Modi, with the next case management hearing set for July 29 - when a timeline for extradition trial is expected to be laid out.

Nirav Modi was arrested by uniformed Scotland Yard officers on an extradition warrant from a Metro Bank branch in central London on March 19 and has been in prison since.

During subsequent hearings, Westminster Magistrates' Court was told that Nirav Modi was the "principal beneficiary" of the fraudulent issuance of letters of undertaking (LoUs) as part of a conspiracy to defraud PNB and then laundering the proceeds of crime.