Coincidentally on Wednesday, just gone, I tried to access a booking on my mobile not via the app which wasn't working and the MMB page asked for a lot more information beyond just locator and surname. It asked in addition for first name, last name, flight number, departure airport, date of flight and flight number. I didn’t know flight number so I never completed the full form and instead clicked on the "return to previous log in form" to go back to old layout.

I just had another go and it appears to be the US website (I am not currently in the UK nor indeed the US so possibly is being driven by the WiFi network that I'm connected to)

https://www.britishairways.com/travel/apis/public/en_us




is this something peculiar to the US or is it going to be rolled out to the UK / worldwide as a new design? It seems a bit more secure to gain access to a booking as it does require a bit more information.