Greenwich University has been in training for years for higher education's heritage coup of the century - its occupation of Sir Christopher Wren's Royal Naval College.

With its collection of listed buildings on 20-odd campuses stretching from Roehampton to the Medway towns, the university has a solid track record of bringing historic landmarks back into use while staying on the right side of the heritage lobby. It is also a dab hand at opening new campuses. Three have closed and two opened in the past two years. Campus fugit, you might say.

"An awful lot of prejudice has been shown against us for planning to use the Royal Naval College," says deputy vice chancellor John McWilliam. "It totally ignores our own heritage, which goes back over 100 years. We were offering degrees long before the redbrick universities had been thought of. It's largely down to prejudice against a former 'poly'."

Mr McWilliam, a trained surveyor, has turned Greenwich into something of an expert client for construction services. The university sector's first major Private Finance Initiative project, a set of student residences, is just a stone's throw from his office. He has a long-standing practice of commissioning rigorous and detailed user-specifications for standard university buildings from "teams of expert users" - his own students.

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When it comes to dealing with English Heritage, official guardians of all that is old and delightful but inappropriate for its purpose, Mr McWilliam knows that the dialogue always starts from the premise that you cannot change anything.

So Greenwich and its consultants have become adept at building facilities as installations that leave their historic hosts untouched. The design team of Dannatt, Johnson Architects and structural engineers Michael Barclay Partnership, has worked on its campuses for 20 years. In recent years they have devised a variety of structures that could, if required, be dismantled and removed without trace.

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At the Dartford campus - formerly the women's physical education college which gave the world the gymslip - they designed a system of self-supporting plywood terraces to create a 240-seat lecture theatre within the gymnasium; the internal structure is fixed simply to the existing floor.

And within a Grade One-listed interior on the Roehampton site, the engineers produced a steel subframe structure to support another fully-equipped theatre which was not allowed to touch the existing walls at all.

Their most spectacular interior, is the library at Avery Hill, built as the great hall of a mansion residence for the Victorian "nitrate king", Colonel J. T. North. A mezzanine gallery has been inserted successfully which, again, makes no contact with the building fabric but which doubles the amount of usable space.

Ironically enough, it is the project for the super-sensitive Royal Naval College site that has allowed the engineers to push their skills to the limit - with a massive hydraulic jack system. Thanks to a wartime bomb which cleared a corner of the neighbouring Dreadnought hospital, the university has a site earmarked for a very large 325-seat lecture theatre. One option being developed at Michael Barclay Partnership is an innovative structure that would enable the entire floor to be tilted as a single slab. This would allow raked seating to be removed and the floor to be lowered to the horizontal.

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Greenwich expects to sign the lease on the Royal Naval College site this summer. When it finally moves in, its two celebrated interiors, the chapel and the remarkable Painted Hall, will be retained by a newly created trust and kept open for public use as at present. Most of the rest of the main complex is, says McWilliam, very unremarkable and should provide good teaching spaces.

Built as alms houses for old sailors and known as Greenwich hospital, the building was conceived as the Navy's response to the Army's Chelsea barracks. Most of the interior spaces are very ordinary dormitories, but on quite a large scale.

Currently used as the Royal Navy Staff College, the complex is full of students, albeit students in uniform - apparently no problem for the heritage lobby - and is a rabbit warren of partitioning. The university hopes to rip most of this out and reinstate interior spaces unseen for over 100 years.