mortar line separation crack in curving garden wall n what to do?

Villaines

Wall is about 12 metres long, 1.5 metres high (neither measured), curving 90 degrees think it's called stretcher bond (?), maybe ten courses high one course wide red brick, there is a crack in mortar line about 3 courses down on peak of curve, about 2-3 metres long, can see light, then another separation line one course up viewed from concrete path outside.

Does not appear to be any danger of collapsing or anything but wondering what can/should be done here, tis a nice wall otherwise, would only repair or do like for like.

If answer is do nothing, what if anything should not be done to avoid further degradation?

Will try to take a few pics.

jack of all

Pictures are really required here, but depending on the location and direction of the cracking it may be possible to build a new pier up against the wall, tying into the existing wall with galv. steel straps or ties. It will be necessary to pour a new concrete pad to support the pier. About two days work I'd imagine.

Edmond_Dantes

curving walls always cause trouble eventually