Sadly, like many of the photos in the suitcase, I don't know who is pictured here or when it was taken. However, the setting does look very much like Calverley Grounds in Tunbridge Wells, Kent.
This area of the town has quite a history attached to it. Calverley Grounds originally belonged to Mount Pleasant House, where the future Queen Victoria regularly stayed between 1826-34.
In 1825 the land was purchased by a property developer. His architect, Decimus Burton, went on to create a new town which was designed to rival the nearby Pantiles. In 1837 the house was converted into The Calverley Hotel (now Hotel du Vin) but the meadows were preserved as an informal open space.
Tunbridge Wells Borough Council purchased the land in 1920 and added a bandstand, sports facilities and created the formal gardens we know today.
A sundial was installed in the rose garden in 1924 and I assume it is the one pictured here. I like the fact that the children are so smartly dressed and imagine a photo opportunity was quite a rarity.