Finding the perfect engagement ring can be a daunting process, so we sat down with diamond expert David Allen, of jewellers 77 Diamonds, to find out what shoppers need to know before they part with their cash.
Carat, cut, colour and clarity are all important factors to consider when looking at a diamond, but there are in fact three other "C's" you need to think about. So if you're a groom-to-be and about to propose, read on for David's top tips...
"The most well known "C" is carat," said David. "It's a diamond's actual weight, not size. One carat equals 0.2grams. Naturally the bigger the carat, the bigger the diamond, but something we like to relay is that diamonds are predominantly priced by the carat. There are certain benchmarks at which the price will jump.
"The price between a 0.9 and a 1 carat is almost 30 per cent more expensive, and we're talking weight, not size. We predominantly look at a diamond from face up, so even if there was a slight difference in the depth of a diamond, unless you took it out of the ring and weighed it, you wouldn't really be able to tell the difference."
The average engagement ring in the UK costs £1,800 and the average carat 0.5ct. In London, the average engagement ring costs £3,000 and the average carat is 0.7ct.
Best buy: "It's up to the individual but I would never be hung up on a carat weight," said David. "Actually a 0.9 looks exactly the same than a 1 carat if it has bigger measurements, so why not go for that and save yourself £2,000?"
"When we're looking at white diamonds, colour refers to how white the diamond is. They're graded D to Z alphabetically, D being the most white. We don't sell lower than an L at 77 Diamonds.
"J, K and L have a slight tint to it and you can see it's quite yellow, so they're much more suited to rose gold or yellow gold rings because you have the warmth of the metal, so you don't see the colour of the diamond as much.
"D, E and F is the top bracket of colours so they're the whitest. Side by side the difference between a D and an F is very difficult to see unless you have them lined up against a white background, and again the price difference is substantial.
"G and H look very similar. G is the average quality that tends to be offered by high-end jewellery retailers. An I colour is the average offered by high-street jewellers."
Best buy: "Anything H or above to the naked eye is nice and white. And then it depends on the individual, do you want to pay for that little bit more, or indeed get the best and buy a D?"
"Clarity refers to the impurities and perfections, in and outside the natural stone. The top level of clarity is flawless or internally flawless – that means inside the stone there's nothing wrong with it whatsoever.
"As you go down the scale you have VVS1 and VVS2, which stands for very, very slightly included – in other words, teeny, tiny blemishes.
"Then VS1 and VS2 is very slightly included; both to the naked eye are fine, you would need ten times magnification to see the impurities and imperfections.
"After that you have SI1 (slightly included) – only 50 per cent of the diamonds have no visible inclusions, 50 per cent do. SI2 we wouldn't recommend because only three per cent have nothing wrong with them. And there is such a thing as Included and those types exist on the high street as affordable rings. The diamonds are so included they look hazy and you can't see just one inclusion."
Best buy: "We recommend anything from VS1/VS2 or above."
"Cut is not to be confused with the shape. It refers to the light reflection within the stone. What you want is any light that goes in, to bounce across and come out again and that's what gives the sparkle.
"It's graded excellent, very good, good, fair or poor. Excellent and very good have the same direction of light; an excellent diamond will have slightly more depth so that there's more room for the light to pass through."
Best buy: "What you want is only excellent or very good, because otherwise you won't have a sparkle."
"What you want to know is that you're buying something and not being had. With a diamond it's really important that a diamond comes with the certificate, and even more importantly, that it is independently certified. Some jewellery companies certify their own diamonds which in theory can be biased and misleading.
"There are five main certification boards. The largest is GIA and they certify about 80 per cent of the world's diamonds. They are very strict and set the standard for everyone else! AGS and IGI are the other two smaller certification boards. The other main player is EGL International and EGL USA.
"EGL is a little bit more lenient with how they grade their stones so if you compared a G colour from GIA and a G colour from EGL, the certificate would essentially say they're the same, but in reality they're a tiny bit different. It can sometimes be up to three grades lower. There's no higher board of authority to come in and tell them to stop doing that, but it's well known and well documented in the industry that this is the case for EGL. It's not to say that an EGL stone is a bad stone, it's just something to be aware of."
Best buy: "Getting an independently certified stone is paramount, and knowing which certification is which. The safest bet is to get a GIA-certified stone because they set the benchmark for the industry. Around 90 per cent of the stones on our website are GIA-certified."
"This is the shape of the diamond. There are ten diamond shapes to choose from and they all have their own unique qualities.
"A round diamond sparkles more than any other which is why it's the most popular, but it's also the most expensive because of the way it's cut. When a diamond is rough and you cut out a round shape, you're wasting a lot more of the natural rough stone which then makes the production process harder, however the result is this cut enables light to bounce at such a sharp angle that it produces so much sparkle and lustre. That's why they're the most expensive, because of the cutting process."
Best buy: "My favourite cut is an emerald cut diamond which doesn't sparkle a lot because it's a step cut diamond so there's less light reflection. Pippa Middleton has an Asscher cut which is a square step cut. Angelina Jolie also has an emerald cut. These are really more unique and you're appreciating the cut of the diamond more than the sparkle, which doesn't suit everyone, but it's another reason why people love them."
"Set yourself a price range and have that in your head, so you can balance all the C's out and get something perfect. Some people come in and say they want a flawless D colour diamond – the top quality – and essentially anyone can afford one of those, it just means the size of the stone will be reduced based on budget.
"If you want a certain carat but you don't have the budget, go a little bit under, or look at measurements for shapes such as ovals or marquises because they're not as deep, so you get a bigger size for the carat you've selected. If you compare a one carat oval with a one carat round, the oval is much bigger. A cushion cut diamond is a lot deeper so a one carat is much smaller than a one carat round, but it's a lot cheaper because of the way it's been cut."
Best buy: "It's whatever people want to spend, and remember, the two-month salary price point was a marketing campaign!"