Two-thirds of the dock is covered with a special roof to maintain a stable environment for the hull.

Between 1982 and 1994 the temperature was maintained below 5 degrees C and the humidity at around 95 per cent.

The hull was sprayed with water to prevent drying and to control levels of fungi and bacteria.

Sprays could be turned off for a maximum of just four one-hour periods each day. This allowed reconstruction work to take place.

Longest was a plank seven metres long, while the largest single element was the rudder which weighed 750 kilograms.

Conservation began in September 1994 with Polyethylene Glycol (PEG) being added into the spray system to stabilise the wood.

Small core samples are taken from timbers at three-month intervals and analysed. This shows how deep the PEG has penetrated.

Core samples are also looked at under a scanning electron microscope to check that no degradation has occurred.

When analysis of the core samples reveals sufficient PEG has penetrated the timbers, the spray will be turned off and a five-year phase of controlled air-drying can begin. This is likely to be completed by 2012.

At this stage the humidity in the hall will be lowered from 100 per cent to around 55 per cent. The hull will then be viewed dry in a controlled museum environment.