Whatever they said on the unredacted plans, which had it listed. Storage and ventilation equipment wasn't it? Makes sense for some otherwise-unusable back roo

Whatever they said on the unredacted plans, which had it listed. Storage and ventilation equipment wasn't it? Makes sense for some otherwise-unusable back room. And it wasn't the "sole secret room", a large section of the plans were redacted, possibly because, oh I dunno, they were worried about GCHQ using the information to get access to the embassy? It's an embassy, not a public shopping mall, it's normal to not publish all the internal details. Come to think of it, my aunt's house has extensive cellars, including one back room used for storage that backs up onto the street where the local fibre link runs. Terribly clever of her ancestors to anticipate this when they built the place.