Originally Posted by
LTN Phobia
I thought about checking a bag airside at T5 (I assume it's at the central CS desks?) but it's a relatively expensive alcoholic beverage so a soft bag won't do

I've been using these
http://www.wineware.co.uk/wine-bottle-travel-bag-black with 100% success rate (so far!) and all my luggage is soft sided. They will take a litre bottle of spirits although you'd have to take it out of any box it came in.
I find them handy for packing all sorts of fragile items (eg indulging my passion for jars of exotic pickles that I find on my travels)