It could be a possible fungal growth build up. Something similar happened to the Comet 4 at Wroughton some years back and it had to be fumigated and controled before it was open to public again.

Regards
Mark

The people that where looking after the trident are no longer alowed to look after it.
I have not seen it open for ages, but I was told by the chap in the entrance box that there was some Health and Safety issues with the state of the inside of the aircraft that need sorting before it will be re-opened.
(looked fine last time I went in it though)