Only about 5mm long. Probably Grapholita jungiella (Lepidoptera: Tortricidae). G. lunulana and G. orobana have similar wing patterns but they are not as common, and they tend to fly only in May to July, while G. jungiella flies in April and May. The larvae of all three species are know to feed on vetch (Vicia sp).
Photo taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2010-04-13.
Dichrorampha petiverella also looks very like similar, but I have two reasons for sticking with the identification of Grapholita jungiella. First, the three short black lines at the rear of the wing match G. jungiella better than D. petiverella, which should have just three black spots. Secondly, the above photo was taken in April which matches the G. jungiella flight period of April-May better than the D. petiverella one of May-August.