Re your comments Gardyloo and Serfty.
What really surprised me was that BA-MRU was not able to book even the first segment starting in MRU-- it can't get much more direct than that! And it would have been nice if there is no "A" inventory for the date I suggested (even though it is showing on Expert Flyer) if they had suggested some proximate alternatives. It may be that EF is not reliable as to available inventory- especially for "exotic" locations but in the past I have found it to be quite reliable.