The fireplace started smoking out of its right side. There’s a brick wall that’s supposed to meet the mantel and keep the smoke in, but it has started leaning in, letting the smoke out. In fact all the brick lining, especially in the back, is beyond its useful lifespan and failing.

Note leaning right wall
You might also notice that the fireplace isn’t symmetrical: on the left side the wall meets the mantle head-on, but on the right side it pokes inside the opening.
It was tool time. I acquired the following:

Mason's hammer and rubbert-coated mallet

Even trowel, pointed trowel and fireproof mortar
My plan was to tear down the wall and possibly the rear brickwork, and re-lay the wall so that it meets the mantle like the wall on the opposite side does.

The wall came apart very easily
When I got to the end of the wall, I got a surprise: there’s a opening in the corner of the fireplace.

A roughly 20cm deep hole with steel wires going across it

A closer view
I can’t lay bricks inside it because of the wires, and I can’t build the wall to meet the mantle because then it won’t cover the hole. I’ll have to leave a corner either inside the firebox or at the top of the wall (if I build it the same way it was before). Somebody made a mistake building this thing.

I've taken out most of the back by now, the opening is in the corner and there's also some empty space over most of the right side
I don’t know what the hell I’m doing. To be continued…
bit of a mess you got your self there Sam LOL
jamie