very strong toilet clearer

You need hydrochloric acid. Probably the strongest supermarket cleaner with highest concentration of HCl is Harpic 10x, about a quid a bottle. The stain is basically discoloured calcium carbonate.

Could it not be removed mechanically by scouring ?

Brick Acid. Or for the feint of heart a more dilute version is available from your average DIY store:

If it's limescale it'll be rock solid. You might chip it off but if there's scale you can see it's going to be just as bad on the blind side that you can't get to. Best off with a full de-coke as required.

HG products usually do what they say on the can/bottle

There was a question almost exactlly thesame in the last Sunday Times. Soltion given was the problem was lime scale. So bail out the U-Bend and then put some lime scale remover on the stain overnight. They did not say get a gas mask.

Limescale removing lavatory cleaner containing HCl. Just don't mix it with the ordinary bleach type cleaner or you'll gas yourself with chlorine.

I would try a saturated solution of citric acid crystals (a few quid per kilo on ebay) in boiling water.

Tip it into the water, not against the ceramic, to gradually raise the temperature and avoid thermal shock. Leave for 10 minutes or so, and then scrub. Limescale comes off easily.

If you're worried about cracking with the heat, throw in maybe 100g of citric crystals to the cold bowl water and leave overnight.

(somebody could do the calculation of how much water there is and how much crystal you'd need to make a saturated solution, but 100g is a guess at 'ample')

Theo

email the White House. Mr Trump will know.

I'd normally be mixing it up in a 500ml jug, although throwing in a handful of crystals and a kettle's worth of boiling generally does the job too.

Theo

caustic soda Brick acid

tim... has brought this to us :

Brick acid will do it.

But not at the same time!

Or Brick Acid from a good hardware shop. Chuck in half a bottle and leave it for half a day. Don't let dogs drink it.

Yes as has been said brick cleaning acid is the easiest obtainable, main thing is to use little and leave long enough to neutralise itself, it's fine in the pan but will react with any cement on its way out if still active.

You risk damaging the glaze if you overdo it.

This summer I have noticed a lot more 'limescale' in the loo and also where the kitchen tap mixer spout leaks down over the tap block. I was wondering if they have been adding more fluoride than usual, or maybe even started doing so ?.

Mix those two and you wont have anything that has any effect :-)

And take off the glaze too. Care needed !