My welder weighs about 55kg.
It has a couple of handles.
Does that make it portable?
A: Not unless you are Geoff Capes.
The definition is equipment which is moved while in operation or which can easily be moved while connected to the supply. Nothing about being
designed to be moved.
The pond pump must come under the 2nd half presumably, so what makes anything easy to move, apart from weight, size and relative position of the centre of gravity?
Handles?
My original post should have had a

or something to indicate light-heartedness, flameport was right, it's not tripping the RCD by design.
To answer Gary, I don't know. My welder is an extreme case - not many people would find it easy to move, but are we going to class
anything which can be easily moved by virtue of its weight a mobile appliance? I know that's what it says in Part 2, but should actual handles be a factor?
Just looking around me now - the inkjet printer is easy to move, the laser one definitely not, but neither is expected to be moved whilst connected. And as for the broadband router, that would go into a coat pocket. Downstairs I've got a DVD player, tuner, amps etc - all easily moved when connected to the supply, but none of them have handles. The TV does, but is not easy to move. The gas cooker has a flex & plug for the ignition etc, and when the wheels are lowered it trundles about very easily. Is it a mobile appliance?