Worrying cracks in wall

[cpmcclay]

We moved into our 1920s house in July last year. We had the 'middle' survey which reported a few minor problems - nothing stuctural. The house had experienced subsidence 20 years previously and the front of the house was underpinned then. The surveyor reported no obvious signs of any more movement since.

However, yesterday I finally got round to starting to decorate one of the back bedrooms... Taking off the ancient wallpaper revealed lots of hairline cracks on all 4 walls (2 exterior and 2 interior) and 2 large cracks (1 on the exterior wall to the right of the window and the other on the opposite interior wall). The crack to the right of the window is midway down the wall and is at its narrowest at the window getting larger towards the corner of the room. The crack on the opposite wall is midway down again and spans the whole wall (hairline mostly although about half an inch wide closer to the door). Please see the picture...

There are no cracks downstairs or outside - although the house is rendered so this could hide something I guess?

I'd really appreciate any of your expertise!

Thanks

 

[foxhole]

To be expected in old property, fill and decorate, only time will tell.