I think the visa checks for PRG were another T5 bungle.

Either some penpusher thought that everyone needed visas to PRG, or thought that PRG was the code for Tripoli.

Either way, PRG has been removed from the list of dodgy dodgy destinations, and the list is now DME, LED, KBP (even though most of us don't need visas) and TIP.

http://www.terminal5.ba.com/en/departures/ -
Passport and Visa Check for customers with hand luggage only If you’re flying long haul or taking a short haul flight to Moscow, St Petersburg, Tripoli 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. This helps keep the flow of people through Security running smoothly as any problems will have been dealt with beforehand. If you have baggage for the hold, your passport and visa will be checked at a Fast Bag Drop or Customer Service Desk.