Birds make their exit
Buildings Supervisor Alf Wilson was in for a surprise when he approached F Turnstile because a house martin flew past his ear.
Investigating further, Alf discovered a nest concealed at the top of E005 Emergency Exit.
He said: "We do have them nesting on the fourth floor but these birds had nested much closer to the ground. I watched them for a few days and then saw all four chicks leave the nest."
Alf took this picture to commemorate the event.