Working with Christopher Wren

The refurbishment of King William Court, one of four blocks forming the Old Royal Naval College and framing the famous view of the Queen's House, was unusual in that the two wings of the building were in very different conditions. The original interior of the west range was virtually intact, but little of the interior of the south range remained.

Dannatt Johnson Architects, the practice employed by the university to redesign the interior, had a daunting task. The change in the building's use from a military establishment to civic university is extreme. The building's historical importance meant English Heritage – and the rest of the nation – were watching carefully. The previous occupant enjoyed crown immunity, so modern safety standards had to incorporated from scratch. And the architect's intervention had to stand up next to the work of the three greatest English classical architects.

Dannatt Johnson, though, has not shied away from the janus-faced nature of the project, but embraced the challenge and come up with a suitably contemporary architectural solution in the south range and sensitively restored the west. Walk inside King William Court and the transformation is extraordinary. Large modern lecture theatres with all the latest audiovisual equipment wear their services with pride.

Glass-sided lifts sweep up the building affording a tantalising glimpse of the courtyard through the original windows. In other areas, however, the building is much as it was when conceived, hanging on to interesting little vignettes such as the remnant of a fume cupboard from its naval college days, now at the top of a brand new staircase. This is a solution that surprises and delights, yet gives a real sense of the building's history and original plan.

English Heritage has been firmly in the driving seat throughout the restoration. The Greenwich Foundation was established in 1997 by the Department for Culture, Media and Sport to safeguard the site, and has been responsible for subletting it. EH worked with the foundation to set the restoration criteria before the final use of the buildings was established and a tenant found. This criteria prevented any significant changes to the exterior and limited the removal of internal partitions unless they were modern or it was absolutely necessary. Indeed, EH was keen to see earlier room divisions reinstated.

The organisation was closely involved in selecting an occupant, and steered the selection process towards a use that would minimise disruption to the building's fabric. Anything that would have required high levels of care and servicing for the occupants, such as a hotel or hospital, was discounted because it would have meant significant changes to the fabric and would have been incompatible with the character of the rooms. In the end, an academic use proved ideal. Michael Turner, inspector of ancient monuments and historic buildings at EH, says: "The naval college had lecture theatres, IT and so on, all installed by the Ministry of Defence.

The capability of the building to be adapted in that way had already happened, so we knew it was possible."

Once the university and the architect were selected, they worked closely with EH to satisfy the competing criteria. A conservation plan identifying the principal building phases for King William Court was drawn up as an anchor for future decision-making.

"Everyone started off with the same level of knowledge and understanding of the principal areas where changes could be made and where we should conserve," recalls Turner. Anything remaining from the original naval hospital was sacrosanct; there could be greater leniency with the naval college modifications and a quite relaxed approach could be taken with 20th-century additions.

Much of the west range conforms to Hawksmoor's original plan. A central corridor runs the length of the building. Off this are original cellular rooms, or "cabins" as they are known in deference to the building's naval history; these would have housed the veteran sailors. Original panelled oak screens with glazed areas above (added at a later date) separate the rooms from the corridor. The majority of this was intact, albeit hidden under hardboard and layers of paint. The cabins proved ideal for conversion into offices for lecturers and administrative staff.

This collection of small rooms gives the whole area an intimate – almost claustrophobic – feel, which is relieved by the long corridors. As the building was originally conceived as a hospital, it is very austere without extraneous decoration. Some interest is provided by the motley collection of fireplaces, as each room has its own; these variously date from the origins of the building (see box) to the 1930s.

The main conflict between EH and Dannatt Johnson occurred over the west range. The architect wanted to add a new main entrance, but EH put its foot down as, according to Turner, "it wasn't defensible on historical building grounds". Instead the students enter through a modest existing door in the south range.

Despite this, there are a couple of modern touches. A new staircase for escape only, and two fire screens had to be installed to meet Building Regulations. The small staircase matches the scale of the main access staircase, with minimal impact on the original scheme. The stair is constructed from American oak and features glass balustrades. New screens were inserted across the corridor, as the original could not be upgraded to comply with fire requirements.

Unfortunately, the careful historical restoration is marred by a plethora of petty notices, office clutter and a very utilitarian brown office carpet that would have been more at home in a 1970s office block. Because of this, the most appealing space is an empty room on the second floor that has retained the original stone flagged floor and a simple yet elegant original chimneypiece.

In contrast, the interior of the south range has been radically altered. The navy chopped this about more than any other part of old college, as it was occupied by the Old Royal Naval College department of nuclear sciences. The department didn't hold back from installing some pretty unusual kit, including a working nuclear reactor (see box, page 54) and the control deck of a submarine. To add insult to injury, the MoD ripped out the original screens in the only parts of the building not filled with military hardware, substituting them with their own.

This left little of the original fabric. "This allowed us a more experimental approach to the conversion of the building to teaching accommodation," says David Johnson, partner at Dannatt Johnson Architects. Because there was far less need to conserve the original interior, there was greater freedom to create more generous spaces. Three large lecture theatres and spacious computer labs have been inserted, as well as some smaller teaching rooms. This seems to clash with the spirit of the original design, with its small rooms, but in fact other parts of the complex, notably Queen Anne Court on the north-eastern corner of the site, originally contained large open dormitories.

The lecture theatres are the most radical element of this wing and contrast strongly with the carefully restored interiors of the west range. One theatre contains visible ventilation ducts and air diffusers in the roof space: galvanised steel is juxtaposed with the massive timber trusses of the roof giving the impression of a modern painting in a traditional frame.

Even though the interior treatment is radical, the exterior of the building could not be altered in any way. As tourists can look down on the roof of the college from the Old Royal Observatory high up in the park, any plant on the roof would be highly visible. To avoid this, the boilers were shoehorned into a small room in the attic and the air handling units were hidden in a shaft beneath a laylight above a second lecture theatre. The laylight has been artificially lit from behind to give the impression of daylight filtering through.

New lifts and staircases were also necessary to provide fire escapes and disabled access. A glazed lift shaft passes up through a series of small rooms and integrates well with the space in which it is enclosed. A second lift is parked against a wall in a large, empty circulation space that looks like a giant wood-veneered filing cabinet. Unfortunately, the dowdy effect is exacerbated by the omnipresent brown carpet.

Overall, however, Turner is very pleased with the end result. "It's a good example with what could be achieved with a good architect", he says. "You can do a modern interior yet retain the original where it has survived".

Now the building is fully occupied by students, and the refurbishment of the Greenwich complex is complete. When the lease runs out in 148 years from now, parts of this era will doubtless be preserved for posterity in the next refurbishment. Much will be left to conserve – although hopefully not the carpet.