I really have no idea what this short tunnel/shelter just below the cliff top is for, it seems too neat and too short to be mine related. To me it gives the impression of being a shelter from where the view can be admired. It looks to have been cut by hand.

  

Does anyone have any idea of its age and purpose ?

Just a short distance away to the north, this unusual item is visible by the side of the Cleveland Way, the metal part still freely rotates and there appear to be the remain of powerful springs attached.

It is some distance away from both the Sandsend and Kettleness tunnels.

UPDATE : Dave Richardson has kindly come up with an answer for the second one, its a Motley Mount for Twin Vickers “K” Machine Guns for light anti aircraft defense, there were originally four as the Goldsborough Cliff Radar Station was here from 1940 to 1945.