A lot of games now use SSL for communication between game client and game server. This traffic is being mis-recognised by BT's traffic shaping software as p2p traffic and seriously effecting in-game latency rendering the game unplayable.
There is no way to identify what SSL encrypted traffic actually is as it cannot be decrypted by a 3rd party. So traffic shapers are ALWAYS going to be doing this kind of thing and they are never going to be reliable. Heaven knows what BT have spent on this rubbish, but undoubtedly it would have been better spent on increasing their total bandwidth capability instead of a futile attempt to limit usage on a vastly over-subscribed network and try to pass the blame for this onto heavy users, while meanwhile ruining the on-line experience for many users who are unfortunate enough to enjoy services that are SSL encrypted.
One particular game I play is unusable at peak times because of this system. I am considering switching to SKY who do not have traffic shaping in place and telling BT to shove their contract as they are not supplying the service that I would normally be expected to have.