Mysterious flatworm

Mysterious flatworm

Observation - Mysterious flatworm - UK and Ireland. Description: Very dark brown with three thin, dull yellow dorsal stripes. Underside white-grey. Head end is reddish/orangey and thinner than tail end. The whole thing is about 2.5cm when not moving but up to 4cm when stretched out. Coils up. Leaves a trail of mucus. D

Very dark brown with three thin, dull yellow dorsal stripes. Underside white-grey. Head end is reddish/orangey and thinner than tail end. The whole thing is about 2.5cm when not moving but up to 4cm when stretched out. Coils up. Leaves a trail of mucus. Don't want to let it go in the garden if it is an alien invader.