Thanks; I followed those stairs to find myself in a deserted corridor with entrances but no clear exit. Clearly transit is an abnormal activity at OTP. Rather than draw attention to myself and my rather odd/'suspicious' routing, I checked that they only looked at (not scanned) passports and went through immigration and back in through the departure hall as normal. I had plenty of time as my SWISS flight arrived somewhat early, which helped.

Speaking of SWISS, I travelled on miles in their Business Class LHR-ZRH-OTP and I must say it puts Club Europe to shame; particularly the staff - young & presentable, immaculate uniforms and personal appearance, polite and attentive (my name remembered though I have no status with them; juice topped up without asking; nothing too much trouble) - and no constant wittering/gossiping to each other rather than serving customers (BA staff take note!!!). A credit to their employer. The quality of the cooked breakfast - among the best scrambled egg I have ever had on ground or in the air - also bears remark as well as that of the the Swiss Ticino Merlot with lunch. All this and a Swiss chocolate on leaving. Do BA have secret shoppers sampling other company's offerings? Do they learn from it? It is a long time since I went over to any Dark Side for European business travel and it was an eye-opener!