I think that's Russia and Ukraine? Poland being an EC member state doesn't require visas for EC nationals.
Don't know why but ba.com says Prague is on the list! Looks like a passport check, not a visa.
Passport and Visa Check at Terminal 5
If you’re flying longhaul or taking a shorthaul flight to Moscow, St Petersburg, Prague or Kiev and you’ve checked in online or at a Check-in kiosk at the terminal, you will need to go to one of the passport and visa check desks before going to Security. If you have luggage for the hold, your passport and visa will be checked at a Fast Bag Drop or Customer Service Desk.