Originally Posted by ULTIMATE BA Guide

However, you can get round this, as BA will allow you to MFU (and charge half the miles) if only one segment has availability for the upgrade. Actually getting an agent to book this however, can be quite problematic. It may require escalation, or in the worst cases a PM to our friendly ‘lurker’ Lyndsay (BA Executive Club) to sort out. Generally, if you quote ‘AskBA 1056’ to the agent (which is the ‘AskBA’ article which describes this valid practice), they will relent and be able to book what you need.