Thanks all. Points noted about security and not to pack anything I couldn't bear to never see again in checked baggage. I've purchased a TSA approved lock - one made by "Travel Sentry". It has a 3 digit number thing, and a TSA keyhole that has the words next to it "TSA 005" - do they use, or change, TSA keys periodically, hence reason for them being on No 5 these days?
Thanks for idea about cable ties - I've already got a huge pack and shall take some with me just in case.