The photograph shows an old iron hinge on the wall of Magdelene Chapel on the corner of Holloway and Magdelene Avenue.
Before the development of the Magdelene Avenue estate at the start of the 20th century, this hinge held the gate to the grounds that extended behind and to the side of Magdelene Chapel. The gate is clearly shown on the 1885 Ordnance Survey map of Holloway, see the detail below. Holloway House and its grounds no longer exist, being demolished around 1905 to make way for the Magdelene Avenue estate.
The gate appears on a number of old drawings and woodcuts from bygone days, for example as seen in this 1829 sketch by Thomas H Shepherd
Much of this drawing is recognisable today, including the elevated pavement and even the Judas tree in front of the chapel. This is the same tree as in the modern picture above, although it has now been severely pruned back. It was a mature tree in 1829 so now is over 200 years old. By some 40 years ago, the tree had grown so large that a major branch extended over the chapel wall and over the pavement, having to be supported by a wooden prop next to the road.