Brencud - presumably ambulances use this exit, so it cannot be blocked.
And I suspect the emergency services would object if a set of crocodile teeth were fixed to the top - they might need to take a short cut, and that saved minute might save a life.
I have to say I am still not convinced that this is such a busy ambulance station that it justifies the one-way on MM - I guess we have to take it on trust that Lewisham are doing this for the right reasons.