A couple of guests had expressed interest in the railway so after a bit of gardening I got the VoR loco out and we had a play.
We've found a compromise to the 'water in the garden' problem. The garden is lacking any significant water feature but the railway is occupying the only level area. So, we've settled on a semi-formal pond in the centre of the railway lawn. Formal in the sense of a geometric shape, but it'll be informally planted.
Should also deter football on the railway area, which is a Good Thing.