The House of Commons (image below from Wikipedia) has two red lines on the floor.
Wikipedia states that:
In front of each set of benches a red line is drawn, which members are traditionally not allowed to cross during debates.
These lines can clearly be seen in the picture.
I have been following a couple of live parliamentary debates recently and I noticed that Ian Blackford, leader of the SNP in the House of Commons (the actual party leader is not an MP) regularly makes his statements while standing firmly across the line; see for example the image below (taken from the Press and Journal; purely the first random image from Google Images on which the line and his feet could be seen) which shows both feet inside the line.
This is not a coincidence; in fact, I want to recall Mr Blackford taking this position every time he speaks. Given that a great number of things in the UK parliament are based on tradition and seem weird or unnecessary nowadays, it strikes me as odd that Mr Blackford is allowed what I perceive as a breach of this tradition.
Is there any reason be it written or traditional that would permit Mr Blackford to stand across the line or is it simply permitted because nobody objects?