Slight Bowing Of Flank Wall

[danieljsharp]

I noticed some very small hairline cracks in some internal walls, after investigating further i noticed the flank wall was bowing on the outside.

There are no cracks on the outside of the wall and the bowing appears to be quite small. The house was built in 1900-1910 and is end of terrace.

Should I be overly worried about this or is it a situation which is common in houses this old?

Any help or advice appreciated, Thanks