Buckingham Palace's kitchens have been given a complete make-over in a redevelopment which has effectively sliced them in half and allowed the installation of a state-of-the-art ventilation system in the process.

Located on the ground floor of the palace - which, curiously, is referred to as the basement - the kitchens used to have soaring ceilings about 8m high. "Ventilation was one of the big bugbears over the last seven or eight years, but because of the large height of the kitchen, nothing could be done," says royal chef Lionel Mann, who has worked in the royal kitchens for 41 years, having originally served an apprenticeship in the kitchens of Vauxhall Motors in Luton, Bedfordshire.

Now the problem has been solved through a project in which a new Queen's Gallery has been built, with a lecture theatre on a mezzanine floor created from the top half of the kitchen. This means the new kitchens now have ceilings at the more reasonable height of 3.5m.

Moreover, a Giff ceiling has been installed, so the entire ceiling is ventilated without the need for trunking. Each area of the kitchen is individually temperature-controlled and all the panels in the ceiling can be removed for regular cleaning.

The architect for the Queen's Gallery and royal kitchens project was John Simpson & Partners, while the kitchen design was by the Grantham Winch Partnership. Buckingham Palace is the most recent of the royal palace kitchens to be renewed in the last few years - new kitchens were installed at Windsor three years ago and Balmoral two years ago, while Sandringham's equipment was updated last year. With this experience behind them, Mann, his chefs and the rest of the palace team had a clear idea of what they wanted to achieve at Buckingham Palace, which was last fully renovated in the late 1960s and early 1970s.

Much of the kitchen is located in the same position as before, but some extra space has been gained from former offices, and the larder has been moved. At the heart of the kitchen complex is the Royal Kitchen, or hot kitchen. This is a large, square room with four parallel island suites leading down to two long hot cupboards from Holmes Catering which are used as a pass. A priority was to have all the cooking suites leading down to the pass, whereas previously some were parallel to it.

Another of Mann's priorities was to create a good flow. "I wanted deliveries to flow through raw preparation and then into the hot kitchen," he explains. "The new layout keeps raw and cooked food apart more easily and is much more efficient."

Refrigeration, too, was a big issue. Previously there were two walk-in fridges and one walk-in freezer - now there are three additional walk-in fridges. Also, numerous under-counter fridges have been installed, whereas before there were none at all. Two large Foster blast chillers have been retained from the old kitchen.

The refrigeration plant for the walk-ins and the air conditioning in the kitchens and the Queen's Gallery is unusual in that it uses a geothermic cooling system. Instead of having the usual condensing towers on a roof, cooling is achieved by using water drawn from a bore hole drilled in the palace garden. A maximum of 22 litres of water per second can be drawn to feed the underground refrigeration plant room in the garden. Visually, this system has benefits in that it doesn't require towers to be stuck on the palace roof. But its main advantage is environmental because it helps to reduce London's over-high water table.

At Buckingham Palace the kitchen caters for an extraordinary diversity of occasions - anything from the Queen's lunch to state banquets, from functions for members of the household to food for up to 450 staff. It can cope with up to 350 for functions and up to 1,500 for canapés.

For about 18 months while the new kitchen was being built and installed, Mann and his team worked from a temporary kitchen created within the palace. The temporary kitchen had a raised floor to accommodate power and plumbing. It had ventilation installed and was properly fitted out with equipment from the old kitchen and some new work surfaces. This meant the brigade managed to work as usual, with the exception of four state visits and two diplomatic receptions for 1,500, which had to be transferred to Windsor.

The Royal Kitchen
One striking feature of the Royal Kitchen is the number of historic appliances dotted about, most of which are thought to date back to Victorian times. An old gas oven made by J Slater is no longer in use, but a neighbouring hot cupboard with venerable wooden doors is occasionally pressed into service - though it is more commonly used to store gastronome trays. It was once heated with live steam - which was taken out of the palace some 20 years ago - and has since been converted to electric heating.

In an alcove there is a splendid old gas range, which has been refurbished and has an added safety rail. Its burners are at two different levels, but both are very low, making it perfect for stockpots and large pans. "You can't use too high a pot on the modern stoves because of the fire suppression system," says Mann.

Ambach ranges have been incorporated into the island suites, some with solid tops and some with gas burners. Mann especially likes the design of the solid tops, which are rectangular with a gully around them where any spills drain, to be collected in a drawer underneath. Unlike many solid tops they do not have a "bull's-eye" and are designed to have an even temperature all over.

The two middle island suites have Gram under-counter refrigeration and lots of space for prep work, while most of the cooking appliances are in the two outer suites. Wherever there are cooking appliances in the suites, there is an Ansul fire-suppression system mounted above.

The kitchen complex occupies numerous rooms with corridors running between them, so there are many doors. To prevent them being a nuisance to busy chefs, they have all been fitted with automatic opening devices that operate as people approach them.