Indeed, beezalex.
Gavin, as mentioned above, get the lever one notch or more down at the drum plate side to get the angle within a decent spec., then get rid of the adjuster at the brake lever, adjust the cable at the drum side. On your pic the lever is far past what should already be absolute max possible braking, and as beezalex points out, the loss in braking power will be substantial.
And check the shoe cam action, should not move to a too steep angle (against it's brake shoe contact surfaces) before max braking occurs.