Not only . . .

. . . did I manage to spot a non-white butterfly, but I managed to photograph it . . . and identify it. 

Speckled Wood (Pararge aegeria)
Found in partially shaded woodland with dappled sunlight. That's funny, as that is exactly where I found it (see extra). 

Cliburn Moss National Nature Reserve. Apparently it is a recent colonist of the Reserve.