It's by Daphne Rowles: The Artist's Garden, Hertford Avenue, East Sheen, circa 1930, available from LissFineArt.com for £1,950.
Gardens still looked like this in 1950 and 1960. Quintessentially English and what Roy Strong has called 'comfortable' in style; something which looks familiar to us and feels right. I love it and want to walk along the path to admire the delphiniums. Even so, I wouldn't want my own garden to look like this, nor would I hang the picture on my wall, even if I could afford it.