The £400,000 restoration of York's magnificent Assembly Rooms is proceeding on schedule. STEPHEN LEWIS took a look behind the scenes

THERE'S a wonderful etching, which probably comes from the pages of Francis Drake's 1736 book Eboracum, showing elegantly dressed Georgian men and women attending a dance in the Assembly Rooms.

The Rooms had been completed just the year before, in 1735, specifically as a place for the wealthy leisured classes of Georgian York to gather for dances and other social occasions. So this etching probably comes as close as we'll get to a glimpse inside the Assembly Rooms as they were originally intended to be.

For the last two months, the interior of the venerable building has looked very different. Passersby wouldn't know it, because the doors have remained discreetly but firmly shut. But the whole interior of the building's main space - the 'great assembly room' to give it is proper title - has been filled with a thicket of scaffolding.

The reason? Urgent repairs which it was decided were needed to the ceiling after workmen carrying our routine work on the pillars looked up and spotted cracks in the ceiling.

Ask Italian restaurant, which now uses the building, was closed while an emergency inspection was carried out. The ceiling was temporarily boarded over for safety reasons: then at the beginning of July the restaurant closed again so major repairs could be carried out.

The problem was that the ceiling plaster was pulling away from the wooden lathes that were supposed to support it. Experts discovered that when the house was built in the 1730s the lathes had been arranged so that the gaps between them were too narrow. The plaster was thus unable to grip properly, and after almost three centuries was beginning to pull away.

It was a very similar problem to the one discovered with the ceiling of the State Room at the Mansion House. And there was only one solution: strip away the ceiling, strip away the old lathes, then completely replace both.

That process has now been almost completed. The entire ceiling has been covered with new lathework, and replastered using a traditional lime plaster.

It is now in the process of being decorated.

Repairs have also been done to plaster cornicing. And 11 magnificent Murano glass chandeliers have been taken down and are also being restored - with some new glass being commissioned from a factory at Murano in Italy to replace pieces that were lost or damaged.

Simply restoring the 11 chandeliers will cost about £50,000, says Philip Thake, chief executive of the York Conservation Trust, which owns the building and has commissioned the work. The total restoration bill is likely to be more than £400,000. Looking after York's heritage doesn't come cheap.

The good news is that the restoration work, being carried out by York-based Simpson's, is proceeding on schedule.

The thicket of scaffolding filling the interior of the Great Assembly Room should come down this week. Smaller tower scaffolding will then be used to replace the chandeliers once they have been restored.

"So we're hoping - fingers crossed - that the restaurant (Ask) will be open by October 23," says Mr Thake.

Diners and those simply curious about what has been going on behind the closed doors will be delighted to hear that.

Assembly Rooms factfile

The Assembly Rooms in Blake Street were built between 1730 and 1735 as a meeting place and ballroom for York's wealthy Georgian elite. They were originally to have been designed by William Wakefield, but when he died the job was given to Richard Boyle, the 3rd Earl of Burlington, instead.

The building is thought to be possibly the earliest 'neo-classical' building in Europe, according to a brief history on the York Conservation Trust's website. Burlington based the design of the main ballroom on a reconstruction of an ancient Egyptian hall, while the surrounding rooms and the facade were based on Roman houses and baths.

Then building has been altered several times during its long history. After a fire in 1773, alterations designed by Sir John O'Corall were made in the Lesser Assembly Room. In 1859 a side wall between the Great Assembly Room and two side rooms was removed, to improve circulation; and in 1885 a footpath was created through the portico by cutting away the podium around the columns.

York Corporation bought the building in 1925. The corporation carried out some repairs in 1939, and restored the building more fully in 1951.

York Conservation Trust, which is committed to the preservation of historic buildings in York and now owns almost 100 of the city's finest properties (including the Theatre Royal) bought the Assembly Rooms in November 2002. For some time the building has been used by Ask Italian restaurant, though it is open to the public for viewing on a small number of days each year.