Here are some pictures of the wall. Generally the cement is just a bit like packing there is no adhesive quality. If the coping stones were not adding weight it could easily be kicked apart.
General view of damage after I tied up by putting the bricks back and replacing one coping stone.
There are 5 coping stones numbered from the gate.
No. 1 was dislodged but was fairly easy to realign but the bricks under it are not very tight.
The second and third stones were knocked of the wall. I did put Stone 3 back, yesterday, just to see if could do it and how it sat, but removed it today to clean up the damage as prep for relaying. You can see how ropey the wall is/was under the 3rd Stone.
So when cleaning I removed the bricks back to Stone 4
Stone 4 This had also been dislodged and pushed against the pipes of the air-pump but I don't think it was with much force or caused any damaged. I moved it back to a more aligned position but again the bricks under it are not solid.
So I removed bricks from under Stones 2 and 3. The bottom layer seem fine it's up against the concrete patio.
It's not an urgent job so I can do it at my leisure so no need to get here soon.
23rd Jan 2023
Gavin and I spent a few hours and managed 4 layers. With what is left, some scrappy 15 bricks it will require another 5.
27th March 2023
I managed to use a couple of oversized bricks I brought up and four broken 'half' bricks with one taty brick left over
Gate hook well cemented so re-hung gate. Added some small brick to leaning pillar to limit leaning and adjusted depth to allow gate to close but not to the latch. It could benefit from the latch key being cut back ¼"