In the lead up to Meghan Markle and Prince Harry's wedding on 19 May, royal fans are still taking bets on every part of their big day, from who the Suits star's bridesmaids will be, to what her dress will look like.
However, there's a few things – really odd things, we might add – that we can be sure to see on the couple's big day.
Here are the traditions and rules Meghan Markle and Prince Harry will follow on their wedding day:
1. Meghan's bouquet must contain myrtle
Meghan Markle is staying true to her word and ensuring Princess Diana's memory plays a big part on her wedding day. In order to pay tribute to the 'People's Princess', Meghan has decided that her wedding bouquet which will be made up of white garden roses to symbolise the royal.
White garden roses will also feature in the church floral arrangement, and sit alongside peonies (Markle's favourite flower) and foxgloves, according to the BBC.
However, the Evening Standard reports that her bouquet will also feature myrtle, in keeping with royal tradition.
The choice of myrtle – otherwise known as the 'herb of love' was a trend led by Queen Victoria and every royal since has carried it in their bouquet. Oh, and it won't be just any myrtle, but come from the shrub Queen Victoria planted after her wedding, rumoured to be outside Fulham Palace.
2. The bride will lay her bouquet at the Tomb of the Unknown Warrior
The Queen Mother unexpectedly did this during her wedding to King George VI in 1923 as a tribute to her brother Fergus, who was killed at the Battle of Loos during World War I.
In 2011, Kate Middleton's bridal bouquet was laid at the Grave of the Unknown Warrior inside Westminster Abbey – one of the most scared places in the Abbey which is the only part upon which the congregation aren't allowed to walk – after the Royal wedding ceremony was completed.
It is widely believed that Meghan will follow suit.
3. The groom must wear a military uniform
Stemming from Queen Victoria's wedding, her husband Prince Albert donned a full military uniform for their wedding day in 1840. In the years since, all male members of the royal family – including Prince Philip, Prince Charles, Prince Andrew and Prince William – have worn their military uniform.
Prince Edward is the only male royal since who didn't wear military uniform as he's only ever held two military titles, neither of which he held at the time of his wedding. To wear a military uniform as someone without rank would have been deemed appropriate.
As a result, it will be unlikely that Prince Harry – who served in the army for a decade and completed two tours of Afghanistan – won't wear his uniform.
For his brother's wedding in 2011, the 33-year-old royal wore the uniform of a Captain in the Household Cavalry's Blues and Royals.
4. The royal family must sit on the right side of the church
The Standard reports this is only the case if groom is the one with royal blood. If it is a princess getting married, then the family will sit on the left.
However, this is actually the case for most weddings as hundreds of years ago, kidnappers would often capture and hurry off with the bride in order to steal her dowry. In order to ensure that the groom could keep his sword arm (the right) free, the bride stood on the other side (the left.) As a result, the wedding guests follow suit.
5. Meghan's wedding ring must contain Welsh gold
Traditionally, royal wedding rings are made from Clogau, or Welsh, gold. This tradition dates back to 1923 and the wedding of George VI and Elizabeth Bowes Lyon (the Queen Mother, Harry's great-grandmother).
The Telegraph reports the royal family had been gifted a nugget of gold from the now-defunct Clogau St David's mine at Bontddu in North Wales.
Along with the Queen Mother's ring, it was used to make wedding bands for the Queen, Princess Margaret, Anne, Princess Royal, and Diana, Princess of Wales.
In 1981, Her Majesty was given a further 36 grammes of Clogau gold for future wedding rings - part of which was used for the wedding of Sarah, Duchess of York.
The Duchess of Cornwall also wears a wedding ring made from Welsh gold, as does Prince Harry's sister-in-law, the Duchess of Cambridge.
6. There must be fruitcake
Despite the fact Meghan and Harry have chosen on a lemon elderflower cake by pastry chef Claire Ptak for their big day, it is widely thought the pair will also have a fruitcake.
For the Duke and Duchess of Cambridge's wedding, they had an eight-tiered fruit cake decorated with 900 sugar paste flowers.
Queen Victoria, Queen Elizabeth, Prince Charles, and Prince Andrew all had fruit cakes at their nuptials.
7. There will be a formal wedding portrait
Following royal tradition, Meghan and Harry will pose for photos with the royal family for an official portrait. This will be the first time we see Meghan with all the members of the Monarchy.
Similar to Kate Middleton's formal wedding portrait, it is expected for Harry and Meghan to be accompanied in at least one photograph with their parents, Doria Ragland and Thomas Markle Sr, and Prince Charles and the Duchess of Cornwall (Harry's stepmother).