The RSGB have provided an update on 5 MHz band regarding an exercise by the primary user

Users of the 5 MHz frequencies will know that this portion of spectrum is allocated (by NoV only) for amateur use on a secondary basis, available on the basis of non-interference to other services inside the UK.

Ofcom have indicated that, during the coming days, there may be temporary increased usage of the band by the primary user and thus particular care should be exercised to ensure that frequencies are not in use before calling CQ.