Is the Burka a threat to security? Well it has been documented last year that it breached security in the UK. Don't ask me for a link. You will easily be able to find it for yourselves.
Muslim male had to attend court to answer anti-terrorism charges. He entered the court, if I remember correctly, in western male attire. He exited the court, not waiting for the proceedings to commence in a Burka. He apparently fled the country in said Burka.
No Gromit I am not making it up or have imagined it though, I concede, my memory is not as good as it was .
Another piece of evasion kit in the terrorist arsenal and a two fingers up for the attempts to combat it.!!