If I confessed now after many years of marriage, I suspect it would not go down so well.
For the record, my engagement ring did not cost £50 but I'm sure there are those working to such a budget either through principle or necessity.
We recently did a bit of digging around to see if you can buy an engagement ring for the price of a tank of petrol for our new guide to rings under £50.
If you are rigidly stuck to the idea of buying a diamond ring, and you are superstitious enough to believe that you shouldn't buy used jewellery then your options are - to say the least - limited.
I found two rings on Amazon which ticked the right boxes with a couple of caveats. Firstly, the £45 ring contained a diamond which was either 0.04 or 0.05 carat. That's the tiniest of tiny diamonds and around one fifth of the weight that I personally considered when buying my ring (and I wasn't looking at a BIG ring by any means).
Secondly, as is often the case with Amazon jewellery, the price varies depending on which size you buy. This always strikes me as odd, but is presumably due to an algorithm deciding prices rather than a jeweller called Terrence with a magnifying glass and a waistcoat. Only one of four or five sizes available was within the budget with other sizes costing more like £75.
Still, you are still getting a diamond ring for less than £50, so it shouldn't be dismissed as an option.
The next option is buying second hand. Used jewellery plummets in price at an alarming rate so you could expect to pay £50 for a ring costing two or three hundred pounds. Prices are at their lowest for unbranded jewellery which lacks certification and decent descriptions. The very cheapest rings I found on eBay didn't even have a guess at the carat of the ring.
If you fancy taking a bit of a guess and a bit of a risk then you can pick up something reasonable looking and in budget.
The final option is to avoid diamonds altogether, which either means buying an alternative gemstone (Blue sapphire, Green emerald or Red ruby) or buying something which looks like a diamond but which costs a lot less.
Personally, I'd make it very clear from the start that I had bought a faux diamond...but that's completely up to you.
Good luck, I hope they say yes...