When doing some research into easements, deed of variation, MoE licenses, etc it seems to be the case that if you don't have the paperwork in place or a break clause has been lawfully enacted to end an arrangement, then it's tough for the party who looses the escape.
The courtyard owner never gave consent for the escape to be present in the first place, therefore it's presence is (it seems) unlawful (in property law terms) and he cannot be guilty of obstructing it.
Someone has obviously dropped the ball on this by assuming the route could be used - I've been acting on both sides in the past and it's a pain if you are the one needing the escape.
A Deed of Variation or an easement is the usual answer, it can involve an ongoing 'rent' as well as the fees and charges for getting the other party to agree and draw it up, however it can be a protracted business and in one case I am familiar with the client opted to sell the property rather than try and get a new deed of variation - Despite the premises having secondary escape onto a steel external stair for decades a change in owner to the property on which the escape was sitting (and also used it) revealed that the existing license expired and he flat refused to agree an new right of access