IAN- I do not believe that that is the issue. While yes theoretically almost every row on a BA flight to IST can be Club, unless its a Champions League final match or something similar, BA's Biz cabin generally maxes out at perhaps 7-8 rows, and from my observations is often people buying the ticket as a segment of their long haul trip from the US via LHR to IST. While 20 years ago there were plenty of business people who would regularly use BA on this route there are few that still do so, or like myself only do it id there is a very specific reason. Also I should point out that while TK does change a/c types often, depending on the day it can be up to 4 widebody and 3 narrow body per day, and currently often 777's at 49 seats per flight, plus another 3 flights a day to LGW (which are 321 Neos), BTW all the short haul a/c we are speaking of generally have 5 rows not 4. So if BA at a nominal 7 rows of Club at 28 seats, at 2 or 3 flights a day, equals a general max of 84 seats a day, while TK has up to 287 Fixed seats per day, or sometimes even more as I have seen them run 5x widebodies per day. You are correct as to how the married segments work though as at different times in the past I was able to get O/D flights LHR-(IST)-SIN with stopovers in IST in both directions for not much more than solely LHR-IST.