New figures show the bill for the long-running Diana inquest now stands at £4.5 million, but this is likely to increase as the hearing's last few days are not included.
After the hearing ended last week, the Metropolitan Police said it had spent £8 million in total on services arising from the inquest and the Operation Paget investigation from 2004 to 2006.
The inquest into the deaths of Diana and her lover Dodi Fayed, who were fatally injured in a Paris car crash in 1997, lasted more than 90 days and heard evidence from about 250 witnesses.
The jury returned a verdict that the "People's Princess" and her boyfriend had been unlawfully killed.
The figures revealed that taxpayers shelled out £1.85 million for "external legal services", or lawyers' fees between July 1 last year and March 31.
Running costs were £768,000, video conferencing and special visits totalled £703,000, the bill for IT was £677,000 and staffing cost £234,000.
In one case, funds were used to fly an official to Los Angeles to collect a tape of a telephone conversation involving Dodi and his ex-girlfriend, Kelly Fisher.
The inquest also spent £110,000 on consultancy fees.
Today's latest total also includes costs of £187,000 incurred by the coroner, Lord Justice Scott Baker, and his predecessor up to the end of June last year.
Not included in the total is the Foreign and Commonwealth Office and MI6's legal bills. Both Government departments were legally represented at the hearing and face estimated costs of up to £250,000.
The £8 million spent by the Met Police includes the cost of the legal team who represented the force's Commissioner at the inquest, police protection for the inquest jury, and paying for the Paget inquiry - reported to have cost £3.6 million.
Former Met Police Commissioner Lord Stevens's Paget investigation was launched in 2004 at the request of Michael Burgess, the Royal Coroner, who was then overseeing the future Diana inquest.
The former top policeman published his report in December 2006, rejecting the murder claims that had been voiced by some, including Dodi's father Mohamed al Fayed.
A poll published last week found more than three quarters of people thought the inquest was a waste of money.
The survey for BBC2's Newsnight found 78% of people thought the funds had not been well spent.
Just 19% of those questioned believed the inquest was worth it to discover the truth. Tweet