UK Income Tax issues.
When I returned to the UK, in 1970,after a time in Kenya, with the original East African, the UK Income Tax authorities demanded my log book and my passport, so that they could check how many days that I had been in the UK over the last few years.
Fortunatly I had been on the Comets for much of my time and therefore had not been in the UK as often as the VC-10 guys.
The tax man also did the same thing to several of the Gulf Air guys.
Death and/or the Tax Man will get you in the end!!