Licensing conditions
Apparatus, inspection and closedown
1D2 Recall that to assist interference identification a person authorised by Ofcom may require the Licence holder to keep a log of all transmissions made over a specified period of time.
Log keeping as a general rules is NOT required but many radio amateurs like to keep a log of their contacts and also the periodic tests that they carry out but it is not a licence condition. However Ofcom can require that such a log is maintained which will identify when you were operating with a date and time and with who you were calling / chatting to etc.