On 3 Feb, 10:24, David Hansen wrote:

* You should do. The round blue socket you need should (to the regs)
be fused as a radial, not placed on a ring.

Fixed loads of up to 16A, protected by a suitable fuse or circuit
breaker, can be connected to ring mains.

Agreed, although I'm unsure of the 17th's position on this.

However I don't regard this as a practical option here.

Firstly it's "work" to do it. We're talking about a fused connection
to the existing ring and a spur to the blue socket, not just sticking
the blue socket straight onto the ring. Now if this workshop is
anything like mine in layout (a house-sized CU by the door), that's
nearly as much work as running a whole radial back to the CU. That
also gives me fresh cable, in my choice of size, with no other loads
on it.

Secondly (maybe first) it's important to split the RCD protection.

Thirdly diversity is hard in a workshop - the planer auto-starts the
dust extractor, the plasma cutter uses the compressor too. That's
multi-kW loads kicking in in pairs. Some of the assumptions underlying
the design of the domestic ring just aren't applicable here.