there are no problems transiting through heathrow with ba all the way or codeshare airlines, as the security company collects the gun cases from the aircraft and stores them till they put them onto the departing aircraft. the security people have the gun cases at all times, so if a problem occurs they know which one of their staff had them in their custody during collection and transfer. the problems used to occur in the past when it was the baggage handlers who had control of the guncases .there is no paperwork/documentation required to transit. as with anywhere there will always be "technicals", and i know from previous posts on here foxi seems to think heathrow is an issue , but over the last 35 years i have never had a "technical" (touch wood!!). the only "technical" i have encountered was at amsterdam quite a few years ago when i was with a friend i had booked a hunt for in tanzania, and his cases were left on the ground next to the aircraft and we could see them as we taxied off......they turned up 2 days later. your client cant use stanstead as he would then have to transfer to heathrow and depending on where he is flying from i doubt there will be a flight into that airport. it is possible to transfer between airports ,but you would need to use a firearms courier company to meet you and transfer your firearms to your dept airport, or get a visitors permit , which all adds up to expense and a pain in the ass when you can fly in and out of heathrow.......... the time scale to inform ba you are travelling with firearms i have always been told is a min of 72 hours in advance, but thats the minimum. you need to inform them of cal, type ie bolt action sporting rifle, and make. if your ticket shows zimbabwe as your end destination you wont be allowed to take your firearms, as the british govnt has an arms embargo of any type of firearm to that country ( not sure if that is the same when you dept from usa, but if you start in the uk is the case, so needs checking from that side)