I had just got back from work and was watering the plants in the garden just before dusk. The sky was clear and it was warm. As I was watering I became aware of a strange silence. There was no bird song or any other sounds I would hear on a usual evening. The silence was strange because it was not silence exactly, and the only way I can describe it is that it was anti-sound.So I looked up from the plants and saw a large triangular object sort of sliding in a curve about 200 feet above the house. It it must have been 30 to 50 meters across. It was gun metal grey and had 4 lights on the underside. A large orange one in the center and 3 white ones on the corners. The corners were rounded When I realised it was not a low flying conventional aircraft I dropped the hose and ran inside to get my mobile phone to photograph it. I was gone for literally 10 seconds but when I returned it was no longer above the house. It had travelled to what looked like about a mile away towards the horizon and was disappearing fast. Then, when it was just a small dot in the distance it shot off at an 11 o'clock angle into the sky at impossible speed and was gone. Unfortunately I didn't manage to take a photo, and people don't believe me. But I know what I saw. (It looked very similar to the attached picture).