Shed Workshop Extension Cable?

[Foresty Forest]

I want to use a shed as a workshop. I understand there's regulations about running electricity to it. If I use an extension cable plugged in at the house is this acceptable without permission? I'd be running a light and a small power unit.

Alternatively I've thought about setting up an external plug socket (there's an external box that I could wire into. And running a plugged extension cable from here to the shed?

 

[oldbutnotdead]

Its not really 'permission' that you need, it is ensuring that whatever you use is safe.
How far is your shed from the power supply and how often will you be using the power in there? Would the cable be crossing a public footpath or a back lane or just your garden?
More than 20 metres and life gets tricky- 2.5mm flexible cable will start hitting load limits and volt drop, depending on what your small power unit might be?