On 21/04/2018 22:22, Harry Bloomfield wrote:

He didn't need to hack off, just 'butter' a bit over the exposed tile
edges.

I've been on hundreds of roofs where that's been done and the new mortar
has come off and slid down the roof. The only way to do ridges is to
take the tiles right off, remove all the old mortar, lay a new bed, then
point up.

Bill