NEXT time you are in Museum Gardens, walk past the front of the Yorkshire Museum and stand on the lawn between the museum and the remains of St Mary’s Abbey. Hunt around in the grass and you will come across a little plaque. “Crossing beneath central tower,” it says.

This point marks the centre of what was once one of the wealthiest and most powerful abbeys in the north of England.

“Imagine you’re standing in York Minster, and looking upwards into the really high tower,” says Dr Jayne Rimmer. “That’s exactly what you would have seen here.”

For centuries, the Minster and the abbey dominated the skyline of York. Like the Minster, the abbey was a magnificent Gothic building; its tower soared high into the air above York.

The nave – the ruined northern wall of which is still visible – stretched away to the south west; the choir, altar and ambulatory to the north east. The cloister was on the lawn in front of what is now the Yorkshire Museum: the monks’ common hall and refectory next to it.

In fact, virtually the whole of what is now the Museum Gardens was taken up with abbey buildings: a chapter house, school, guest hall, large kitchen, infirmary and, somewhere between where the observatory now is and the Multangular Tower, the Prior’s hall and chambers.

The Abbot, one of the wealthiest and most powerful men in the north of England, had quarters just to the east of the abbey, the building now known as King’s Manor. In late medieval times, this was very much a part of the abbey precinct, and was entered from near the abbey itself.

“When we enter King’s Manor now, we enter through what would have been the back,” says Jayne, a historian with the York Archaeological Trust.

Then the whole of the abbey precinct was surrounded by a strong stone wall. Some of it – such as the stretch facing on to Marygate – still stands to this day. Other sections, such as that along the river bank, have vanished completely.

The wall made the abbey a self-contained community, says Jayne. The main entrance was off Marygate – on the side of the abbey away from the city.

“And what they were saying by having the entrance here is: ‘we are quite different from the rest of the city’.”

The abbey and its precinct were home to about 50 Benedictine monks and up to 200 servants. And there were very good reasons why they chose to shelter themselves behind a wall.

Unlike some monastic orders, the Benedictines liked to be close to a major urban centre, Jayne says.

The black-cowled figures of the monks would have been a familiar sight around York. But they were not necessarily popular.

One reason for the abbey precinct’s thick walls was fear of Scottish invasion – the walls were greatly extended and strengthened in 1315-187, during the ‘Scottish wars’.

But fear of the people of York seems to have been another. The abbey’s wealth and power prompted jealousy and suspicion – and frequent outbreaks of violence between townsfolk and the monks and their servants, often caused by disputes over property rights.

A sumptuous new book about the abbey and its precinct – St Mary’s Abbey and the King’s Manor, York – researched and written for the York Archaeological Trust by Barbara Wilson and Francis Mee, contains some wonderful examples.

“In 1262 it was reported that citizens of York had attacked the abbey, killing some abbey servants in the ensuing affray and (burning) several houses built by the abbey in Bootham,” the authors write.

By 1350, the disputes over jurisdiction – particularly who had the right to collect tolls in Bootham, the abbey or the city corporation – had become so serious they came to the attention of King Edward III himself.

“On hearing that ‘some of the city are uttering grievous threats of firing the abbey and killing the abbot and convent and their men and household servants, and at other times of crucifying them’, Edward III ordered the mayor to issue a proclamation forbidding illicit assemblies or attempts to hinder the monks from entering or leaving the abbey, moving goods, or buying and selling in the city, on pain of death,” the book records.

Things came to a head in the 1530s. King Henry VIII, greedy to take for himself the wealth and property of the great monasteries, began to dissolve them and seize their property.

In 1539, it was St Mary’s turn. The Abbot, William Thornton, was already on bad terms with the Archbishop of York, Edward Lee. The Archbishop had charged him with being “too familiar with a married woman” – and he was ordered to abstain from relations with her or any other women.

Then King Henry began to demand that large monasteries voluntarily ‘surrender’ themselves – giving up their lands and properties. Abbots who refused tended to be hanged; those who agreed were given generous pensions.

Abbot Thornton knew which side his bread was buttered on.

The abbey and its extensive estates were seized by the Crown, the Abbot and his monks pensioned off.

The lead was stripped from the abbey roof, the stained glass confiscated, the abbey’s other treasures seized. The great Gothic building itself was left to decay, its stone cannibalised for walls and other buildings, its ruins left to moulder.

All except for the Abbot’s lodgings.

The beautiful, u-shaped brick building was turned into the headquarters of the Council of the North: the council of barons and wealthy landowners who governed the north of England on the King’s behalf. It was renamed King’s Manor and it was here that King Henry VIII and his wife Catherine Howard stayed in 1541 when they came to visit the city.

By 1541, the Abbey was already stripped and deserted. Over the centuries, it decayed into the ruin we know today – along with the grounds it had stood in. It was only in the 19th century, when the Yorkshire Philosophical Society brought the land and turned it into a botanical garden, that the Museum Gardens as we know them today began to take shape.

For King’s Manor, by contrast, the story was only beginning. The u-shaped building was expanded into the much larger building with two courtyards we have today. It remained the seat of the Council of the North – effectively the nation’s second seat of power after London – until the council was abolished in 1641.

After that, it was for a time the residence of the Governor of York. In 1833, the Yorkshire School for the Blind was founded there, and today King’s Manor is home to the University of York’s Archaeology Department.

But much of it is still open to the public. Sit in the refectory, and you are in the very room where once the great men of the North attended meetings to administer the King’s law and the King’s justice in the northern half of his kingdom.

“They’d have sat right here to enforce the King’s jurisdiction in the northern part of the country,” says Jayne.

Quite a thought.