Surprised visitor.

Son G and I were having a cup of tea on the patio when he noticed a movement in the nearby border.Turns out it was a 3 foot (1Metre) long Grass Snake sun bathing, but it made off across the lawn to the shrubbery when we rudely disturbed it to take  a few pics. ( extra ) It had a fair turn of speed in a wiggly fashion. I last saw one in the garden over 20 years ago, and wonder how it gets in from the woodland behind. Do they shin up walls?