AC - again.
The golden rule it that you always answer the question and you never lie. With the exception of irrelevant detail, you also never voluntarily divulge anything not pertinent to the direction you want things to go. Fortunately no one ever asked me "what don't you want me to know", though my response would have been lots and lots of true but irrelevant detail.
I didn't deal with the Inland Revenue. A colleague of mine did as it was his speciality. He knew the tax regulations about 100 times better than any team HRMC ever assembled so everything was to the letter of the law. He just explained to them how little tax we were paying based on their myriad of rules and our corporate structure that was designed to follow all the rules whilst minimising tax liability. Every big multinational will have people like him.