We aren't sure of the exact situation you are describing as we don't know the terrain/habitat, etc., but there could be several scenarios.

If there is a lot of a vegetation in the area, then the swan may be nesting. If there is no vegetation, no water in the immediate vicinity and no other swans, the swan could be injured or sick. You might contact your local RSPCA or Swan Lifeline in Eton to check on the bird. The last thing we would want to happen is that the bird gets into traffic and gets hit by a car. In fact, this would the scenario for an injured swan. Please let us know how this situation progresses. The Regal Swan