We think Dad took this photo in 1951 but cannot be sure. He took a number at that time when visiting the Festival of Britain that was held at the South Bank that year.
The steps were built around 2003 and are not shown here so that may give a clue. It is also around the time when Dad took photos of St Mary Le Strand and I used car number plates to date those - I assume it was on the same photo trip.
Photo taken by me on the morning of Sunday 17th September 2017.