Large blundering insects are also known as May-bugs which are attracted to artificial light and fly into houses or collide with windows on warm evenings in May and June.
The adult is 20 to 25mm long with a heavily built brown body and wing cases with the tip of the abdomen bent downwards.
Despite a rather formidable appearance, the May bug is harmless and is only a minor agricultural/amenity pest.
Close windows if you leave lights on at night, or proof open windows with insect screens.