The BBC's Lucy Atherton: "It took all the strength of the archaeological team to lift the lid of the tomb"

Archaeologists discovered the fully-intact skeleton in several layers of mud when they lifted the lid on Wednesday evening.

The expensive nature of the coffin and items left in the grave have led archaeologists to believe the skeleton could be that of the most important Roman person ever found in Britain.

The stone sarcophagus, with a sealed lead coffin inside, was buried in the early fourth century. It was uncovered a few weeks ago during the redevelopment of Spitalfields market near the City of London.

The London Museum's archaeological team wore protective suits and masks to open the coffin, in case any bacteria or toxic vapours puffed out.

When the lid was removed, no gases came out - what was revealed was a well-ordered skeleton. The left arm was folded across the chest, suggesting a Christian burial. The ornate scallop shell decoration on the outside of the lead coffin had been thought to be pagan symbols.

The archaeologists were most excited by the inch of mud in the bottom of the coffin, suggesting it may have been waterlogged.

This layer could preserve organic matter and a bundle of leaves have already been found, possibly the remains of a funeral wreath. Other bumps in the mud, possibly jewellery, are being carefully excavated now.

Osteo-archaeologist Bill White said the skeleton was probably that of a woman, possibly in her 20s.

The coffin has been opened around 1,700 years after the woman's burial

He said she would probably have been the wife or daughter of somebody very important, rather than important in her own right.

Scientists worked through the night analysing the find, and more details are expected to be released on Thursday.

It is hoped that DNA tests will establish exactly where the woman came from.

There were no immediate clues to her identity, but archaeologists said further investigation into the coffin's interior might reveal more.

Curator Jenny Hall says the find is unique

Burying such a heavy object around the start of the fourth century AD would have been a rare and expensive event. It was found six metres (20 feet) down in a Roman cemetery in Spitalfields.

"This coffin without doubt belongs to someone very important," says Dr Simon Thurley, Director of the Museum of London. "We know a huge amount about Roman London, but very little about the very, very important people who governed it."

The revelations from the coffin are expected to give new insight into the ruling class of Roman London.

Dr Simon Thurley explains the significance of the find

Very valuable "grave goods" have already been found alongside the sarcophagus. These were placed to help the deceased on their journey into the afterlife.

What we found is very interesting and is unique to this country," Jenny Hall, the museum's Roman Curator told BBC News Online. "Amongst other things, we found a little jet box and a long glass flask which probably would have held perfumed ointments."

The stone sarcophagus is 2.1m by 1.2m (seven by four feet), but the lead coffin is only 1.5m long (five feet).

The former site of London's Spitalfields Market is being redeveloped

The bones themselves will, after analysis, reveal the diet and health of rich Roman Londoners.

Members of the public can view the continuing work on the coffin and the skeleton at the Museum of London until 24 April.