CHRIS, S.73 of the Public Health (Control of Disease) Act 1984 states about Crown Property,
"(1) This section applies to any house, building or other premises being property belonging to Her Majesty in right of the Crown or of the Duchy of Lancaster, or belonging to the Duchy of Cornwall, ***or belonging to a government department,*** or held in trust for Her Majesty for purposes of a government department."[emphasis added]
I'm sure I seen somewhere that for it not to apply, the relevant local authority has to be notified that it is Crown Property.