Whittington Park's hidden mural

Whittington Park near Upper Holloway Station is just a short walk from my house. I often go there to sit, meet friends, relax, attend events or just people-watch.
I met a friend for some tea and cake at the park's cafe recently and then showed her the little wooded area that abuts the back wall of Yerbury Primary School. Walking through there in the past I had half-noticed that there was paint on the walls but hadn't ever taken a closer look. Jen always has a camera hanging round her neck and so we investigated further.

The first two rows show the mural.
The images in the bottom row show the construction of some hideous container-style apartments being built along the Wedmore Street side of the park, some lovely meadow flowers and thistles, and a tree with a face.

On closer inspection we found, hidden behind the climbing plants and graffiti, an old well-painted mural depicting people partaking in different kinds of sport. The only ones we could identify easily were table tennis and football. A woman in a striped dress and hat may have been intended as a spectator or just a park-goer.
I have no idea how when this mural was painted but suspect it's at least 20 years old judging by the Gary Lineker style shorts on the footballers.
Any info welcomed.