A cup of cha and a biscuit goes a long way. Don't be too gushing when in conversation, just try to be yourself, be honest and you will be fine.
As my FEO was a shootist, his visits usually lasted a couple of hours, he could scoff a packet of biscuits and three cups of coffee, easy. Mind our discussions went from Safari in Africa, to Stalking in Scotland and on to Clays on a Sunday morning. Never had any variation refused, and I could take my Cert to Police HQ in Sheffield, and wait until it was done and then come home with it.
I bet it's not like that these days.
Phil*