Cracks following extension

[s154]

We had a single story extension 2 years ago on our 1920s house. We have noticed a few cracks appear internally and externally but not sure if usual settlement (clay soil) or anything to worry about? Any opinions please?

The ones running along the edges of the wall joins look quite normal for plaster drying out and shrinking a but but the ones above and below that window....is it the same window? Are a bit more worrying. Is that part new part of the existing house?

Thanks, these are all the back of the old house so not fresh plaster . The window in the old house. I think the render and windows are 40 years old which won’t help!

Having the extension built could have affected the water table under the original house, which might cause some movement. Are the cracks the same side of the house as the extension, or the other side?

The extension is the back of the house and this external crack is on the left hand side and internals are above where chimney removed. As it’s clay soil we expected some movement so unsure if this is usually

I had similar it was the house resettling after the back of it was taken out and lintel put in