Thank you John Walker.
Unfortunately the Subway Tunnel was sealed off when the current Granville Theatre was built in 1947.
They excavated down from previous ground level wooden Pavillion, which was a temporary structure from 1908.
Needless to say the owner of the Granville Hotel was not amused. Others had covenants that forbid any structure obstructing their veiw and took the Council to Court for compensation. The covenants were set up by Lady Agusta in 1838.