There actually is a legal requirement (brought about by the above mentioned 'Bentine' story) for you to leave basic details of your intended flight with a 'responsible person'. Additionally, some airport operators require you to 'book out' for each flight, in some cases by telephone in advance, but most accept an RTF call.
Don't forget that military 'booking out' differs from the civil version in that your details will be passed to your destination and they will be told when you are airborne.