Ectoedemia albifasciella

There are four species of Ectoedemia which mine the leaves of deciduous oak but this is the only one around at the moment (many will already be vacated). If the larva is still present it has a pale head.

The mine typically starts as a narrow linear gallery that follows a vein and is later absorbed into the blotch but the linear frass can still be seen. The gallery occasionally doesn't follow a vein as can be seen on two of the mines in the leaf below.