Complex sentence: In 1872, it was removed from there to the North Transept (as all the galleries which had filled the church were being removed), where it was rebuilt in a new case and enlarged to three manuals by the firm of J. W. Walker of Ruislip.
Split into simpler sentences: In 1872, it was removed from there to the North Transept as all the galleries which had filled the church were being removed. Here it was rebuilt in a new case and enlarged to three manuals by the firm of J. W. Walker of Ruislip.