Heathrow Connecting Flights at Terminal 5 (separate tickets both on British Airways)

https://www.heathrow.com/flight-connections

This should help you figure out your situation.

You always go through security transferring at a UK airport unless you have come from another UK airport as the CAA does not take on trust the passenger screening capability of any other country.

You can however pass through the immigration area reserved for transfers to flights within the Common Travel Area.

So if I only have a carryon suitcase I won’t have to go thru security again. Even if I have separate tickets London on my phone?

No, you weren’t reading carefully. You will go through security again no matter what.

When you get off your plane, there will be clear signage (purple) that say flight connections. You will follow it to the flight connections center. There are two lines there. The first, for U.K. and Ireland connections is the one you will join. There is also a line next to it for international connections. Your passport will be stamped, you will scan your boarding pass and have a biometric reading done, then get into the security line and go through security again. After security you are in the terminal area airside.

A couple of cautions. Have your liquid bag and tablets/ computer ready to pull out of your bag. Make sure you don’t have any drinks that you picked up on your first flight with you. I’ve never had Heathrow security take longer than 10 minutes except for the time I forgot I had put water in my water bottle during the previous flight......

Tanks so much for the info.

UK security does not allow you to have a separate bag of liquid/cream medications. Everything must fit in the 1-quart toiletries bag.