The House in Nightmare Park (1973)

This movie is what would happen if Frankie Howerd and Hammer Films had a love child. Less spoof of Hammer Films and much more like watching the main character react the way most of us actually would if we found ourselves in such a movie.

In 1907, an actor is invited to perform in an isolated country house, and becomes involved in mysterious and dangerous events.

The film could be a straightforward comedy thriller, if it wasn't for some suitably nightmarish touches and a few grisly deaths which elevate it to Gothic horror territory. At one point the entire family dress up as living mannequins for Foster's benefit, which is frankly bizarre (until you've seen respected horror stalwart Ray Milland do this, you've not seen Ray Milland). Later Foster goes for help in a deerstalker and cape through the fog shrouded moors, which brings to mind Hammer's 60s Gothics. Deaths include scythings, cleaver-ings and snake attacks, and there's even a cringe-inducing mad dentist scene. Tack onto that a great double-twist ending and a striking final image, and The House In Nightmare Park becomes much more than the sum of its parts. Very funny, very Hammer (not surprising when you find out it was directed by Peter 'Demons Of The Mind'
Sykes), and very, very good.