The garage should have two more lintels than it actually did have.
The one lintel the garage did have was in the wrong place.
They builder of the garage must have been running out of cement towards the end of the build. Top courses were held together with a 0.1% cement to 99.9% sand mix.
At some point someone thought it would be fine to cut off a cable and tuck it into the wall. Luckily I thought it may be an idea to put my multimeter on it and check. Yeah, live.
And finally.... Never, ever, ever get me started on a "Cavity Wall Insulation" rant.
Just pull out any loose bricks.
Stop when you get to firm courses or the bottom of the footings, whichever comes first.