How to fix this cracked garden wall?

[Green33]

I hope this is the right place for this.

I noticed a concrete wall in my garden has a full thickness crack through the centre and the rendering was coming off. After striping off the lose rendering I was left with the attached photo. The wall is about 10m in length and about 2.5m high. There aren't any other cracks and despite being a retaining wall (soil on the other side comes to about 1m high) there's no evidence of it bulging. I've got similar walls around the rest of the garden with no cracking although they have support pillars. Ideally I'd like to repair this and rerender it in a way that matches the other rendered walls but I'm aware it might be due to expansion and shrinking of the concrete. Is there anything I can do to fix it to ensure no further cracking and preferably allow me to make it look like the others?

Thanks

 

[Alastairreid]

A wall that length would need an expansion joint built in, you have one now.

 

[Green33]

Is there anything that can be done to enable me to improve it's appearance? If i just fill it with expansion joints filler I'm going to be stuck with a visible crack and a wall I can't render.

 

[Alastairreid]

An expansion bead can be fitted before rendering.