It seems clear, from the description of events given earlier in this thread, that those standing in the fourfoot were given no permission to do so - indeed, the charter train had only just come to a stand, if the first hand accounts are correct. No member of railway staff, including stewards, should be giving permission* for members of the public, or anyone else, to stand in such a dangerous permission - certainly without arranging for the opposite line to be blocked (the only way to be sure that no train should approach, legitimately at least), and even then not without the correct permits, induction, PPE and so on.
* - just to be clear, there's nothing to suggest that any such permission was given, but rather that the stewards acted quickly to clear them from the line.