R107 Distributor cap removal

[Gilesimp]

First job I come to do on my, new to me, R107 and I fail!
I have a 1986 300SL (R107), I can't understand how I can undo the lower bolt on the dissy cap.
The top two have good access, no problem. The lower fixing can't be reached with a normal size Allen key socket, but an extension means your ratchet clashes with the fan & fan cowl.
So can someone tell me the knack?
Cheers, Giles

 

[carat 3.6]

You need to use a set like this, but drive it with a 10mm spanner slid over the hex key.

 

[Gilesimp]

Thanks, I'll give it a go.
Cheers, Giles