Our 20-yr-old hall lights came with dimmable 200W halogen R7s - we have 8 fitted thanks to our electrician's zeal and the odd layout.

Now, in an an attempt to save energy, I've replaced them all with 20W LEDs which work fine even if the overall illumination is a tad less.

What baffles me though is the behaviour of the mother-and-child lamp in the living room which has a maximum 300W R7 halogen allocation - on inserting one of these 20W LED jonnies the lamp becomes "on" by default, even before I have switched it on!

It's not much more than a glow but it's definitely not behaving in a similar way to our hall lights. Could it be connected to earthing?

Sounds like it's either ghosts, or russians.

Well it's not April 1st so it must be 31st October

A Scotsman with eight lights on at once !

You are going soft.
Come down to Yorkshire and get your purse strings tightened.

I don't think it's to do with earthing. What's happening is down to induced voltage - or phantom voltage if you like. When you have two wires running close to one another over a distance, if there are volts present on one wire, a corresponding voltage is induced in its neighbour. This often happens when you have 2-way switching - the 'strapper' wires connecting the two switches are to blame. With traditional bulbs this doesn't matter - as soon as you connect a load, the induced voltage collapses because it can't supply any current - or only a very tiny current. But the LED lamp needs minimal current to work, and the induced voltage is sometimes sufficient to make them glow dimly or flicker into life occasionally. You might find that if you leave one halogen and one LED bulb in your lamp the glow stops.

That's interesting, thnks.

I guess the lamp's tall shaft is the culprit then where the wires must be in close proximity in addition to their snug position within the cable from the plug. Trying to rewire the appliance seems like seriously over-engineering so the solution seems simple; keep it switched off at the mains

Yes if it's on a plug that must be the simplest solution

Wink is spot on: it's a small voltage induced in the wiring - you sometimes see it in LED table lamps which can glow in the dark.