I flew back to London from the US last Friday, March 13. I moved my flight forward after the travel ban was announced.
I couldn't complete my check-in online because BA needed to see my travel documents. When I checked in at the airport, I expected the agent to ask to see my passport and BRP, but she only asked for the passport.
I was starting to get less concerned about carrying my BRP with me during international travel after several trips when I wasn't asked for it. To anyone who's had the same experience, please heed the advice from the experts on this thread and carry your BRP with you whenever you travel internationally.
As an aside, I'm so glad I moved my flight forward. I felt very relieved when I reunited with my husband at Heathrow, although it was hard to say goodbye to my elderly parents who are in a high risk category for coronavirus.
Sending a virtual hug to all the forum members as we deal with this pandemic.