Repair options

I considered chasing three or four deep grooves across the crack using an angle grinder (like electricians do when inserting conduit into a wall, but deeper), then inserting suitable lengths of rebar into each and caulking them with a strong plaster mix. But angle grinders scare me witless, having seen the injuries they can cause in several accidents I’ve investigated in my professional line of work, so I rejected the groove and caulk idea and decided on a more timid option.