We have a roof that is tiled with curved interlocking tiles which have a
profile like a very shallow sine wave. The mortar alongside the sloping edge
of one side has started crack and come out, and I notice that a few of the
tiles on that edge have crumbled leaving only edge closest to the mortar.

What is the trick for removing some of a vertical column of tiles to replace
them, without having to remove the ones beside them to reveal the peg that
each end tile is hooked onto (or the nail that is fastening it to the
rafter), and then remove the column next to that, and so on ad infinitum?


https://i.postimg.cc/y8BT2YnX/Scan-13-05-2021-1358.png is a sketch of the
roof, a single-slope (ie not ridged) roof on a brick lean-to that is
attached to a much larger garage.