LH - OneWorld's latest recruit?

As has already been mentioned, you only need a plausible excuse, assuming your reservation/ticketing takes you further on. On one occasion, my first grandchild had just been born in London when I was due to pass through LGW. That was genuine, but you can easily have 'virtual' grandchildren, nieces, nephews, etc. The recent birth of one's own children in an intermediate point might, however, be considered unusual, and even more so in the case of female pax!