Multiple incorrect responses in this thread. Please read:
http://www.britishairways.com/en-gb/...|||||L2|||||||
Infants who become children while travelling
If you're travelling with an infant who reaches the age of 2 during their journey, your child will need their own seat for any flights on and after their 2nd birthday. We won’t charge you extra for this; you'll only pay the infant fare for the entire journey.
This booking can't be made online, so contact us and we'll be pleased to help you.
BA rules are rather generous but they can lead to this kind of unfortunate situation - more relevant stuff here:
http://www.flyertalk.com/forum/briti...ng-travel.html
You can write to BA - i have no idea what kind of compensation considerations they have.. i assume this is also regulated so BA may get fined for violation... It may be worth posting this in BA sub-forum - folks there may be more familiar with BA specific customer service complaints.