They tend to prefer the middle of the summer when the weather's better for unofficial holiday. They're a bit later than usual this year, but the LU strikes are back. Londoners must be sick to the back teeth of the RMT.
http://www.bbc.co.uk/news/uk-england-london-11064903
7 September is off peak for holidays isn't it.
It is also too early for the new-students-going-to-college.
Perhaps something of which we know not is happening that week and this is our advance warning.
I have noticed that plane strikes seem to occur at bank holidays but hadn't yet considered the matter of London transport as London Is Evil.