How best to dismantle pierced block wall

[alexfromnewport]

In my front garden I have a lovely little row of box that I planted two summers ago behind a two course pierced block wall. The plan is to dismantle the wall when the box hedge is robust/big enough to serve as a substantial enough hedge to adequately screen, or begin to screen, the garden. See pic which is taken looking out and you will see the wall I'm on about - the box is now much higher and chunkier so the top course at least is ready to go

Question is how best to do it? I don't necesarilly want to take the second course down with it - the plan was do one row this summer and another next to offer a bit more protection while the hedge grows even more into next summer. Do I just whack the blocks with a lump hammer, or would it be best to nibble a bit of mortar out of the joints to weaken the structure first. I certainly don't want to squash my plants, so I'll be working from the garden outwards, but neither do I want the whole wall pushing over: the blocks sit atop the original victorian redbrick garden wall, the height of which you can see between the foliage. Am I in any danger of doing any untoward damage to the wall on which the blocks sit?

 

[Newboy]

4" bolster and lump hammer. Work from the end of the wall along it's length rather than the front - there's less chance of disturbing the lower course. Bolster horizontally into the mortar bed as it should be weaker than the blockwork.

 

[r896neo]

New boy is right, go at it from the side.

Screen blocks have notoriously bad adhesion and are often easy to get apart, unfortunately this applies for your bottom course too. The only way to be really safe is to cut the long horizontal joint with a stihl saw. Not an easy or pleasant thing to do if you've not used one before though.

Go carefully and aim for single large confident whacks rather than lots of little nervous taps.