Help with vile toilet

[UnconsideredTrifles]

When we bought the house, the toilet bowl was stained brown. I've tried bleach, scrubbing and a range of toilet cleaners, but nothing's shifting it. DH thinks the colour is a reaction to something in the pipes, rather than excrement (and I hope he's right!) - but does anyone have any idea how to make it white again?!

Harpic Power Plus Tablets does the job for my toilet and limescale.

The Harpic in the black bottle for normal cleaning

Steradent (denture cleaning tablets, come in a tube) for overnight stain removal. I pop 2-3 of them and let them sit overnight. Removes stains easily.

My dd's apartment had a toilet with a huge amount of limescale build up.

Best thing I found was to gently scrape off the excess firstly with a scraper for a ceramic hob, ( similar to a paint scraper), and then threw down a load of BarKeepers Friend powder. Left for around 15 mins and then scrubbed with a silicone toilet brush.

Came up like new!

Thank you all! So many ideas.... I think we are in a hard water area, and it is all below the water line.

I shall try one thing at a time - caustic soda sounds dramatic so I think I'll start with that!

We had this when we moved in (super hard water area). Brown stains all below the water line, looked awful. Harpic Power Plus tablets worked like a charm, you have to leave overnight and then scrub in the morning. I'm scared of caustic soda!!

We have the same problem in a hard water area @UnconsideredTrifles.
I tried lots of bleaches etc. I have found that emptying the bowl, spraying with Viakal and leaving for an hour, then a good scrub does most of it. Then flush, empty the bowl again and this time put a couple of sachets of Oust descaler in, top up with very hot but not boiling water, leave for an hour. Give it a good scrub with the toilet brush and flush again.
That should do it.

I live in an incredibly hard water area and have this problem
I second the use of citric acid powder
Bonus is it's non toxic
I first discovered it for use in my babies steam steriliser 26 years ago!
Very cheap too

I've also read that coke doesn't work for this kind of thing
You're right - it doesn't . I poured a bottle ( from a takeaway delivery , down the loo is the best place for it) it stained my limescale even worse

Astonish tablets ( I buy in Lakeland Ltd) overnight and a good scrub with a silicone loo brush .
Result

Sterodent tablets (the false teeth cleaners). Seriously!