Media playback is unsupported on your device Media caption Canada's Governor General lightly touched the Queen on the elbow as she descended a flight of steps

Canada's governor general has been forced to defend his actions after a "slippy" carpet led to a breach of royal etiquette with the Queen. But how do you avoid a protocol slip-up?

David Johnston raised eyebrows on Wednesday as he was seen to be lightly touching Her Majesty's elbow as she descended some steps, at an event in London.

Mr Johnston said he was simply concerned about the Queen's safety and made the judgement that a breach of protocol was appropriate "to be sure that there was no stumble".

To avoid any future mishaps, however, here is a reminder of the traditional dos and don'ts.

Do:

Image copyright PA Image caption Prime minister Theresa May performs a curtsey as she greets the Queen

Curtsey or bow (the head only) - although you can also shake hands or do a combination of the two as demonstrated by Theresa May (above).

Use the right greetings. On presentation to the Queen, the correct address is Your Majesty and subsequently Ma'am, pronounced like jam.

Be early. Guests should arrive before a royal.

Take the Queen's lead. Don't talk unless spoken to, sit until she sits or begin eating until she does.

Form semi-circles. If you are presented to Her Majesty at a Royal event it is likely you will be marshalled into position in a series of semi-circles rather than straight lines. Guests should try to be empty-handed, Debrett's adds.

Don't:

Image caption In 2009, traditional protocol was breached when the Queen and Michelle Obama were spotted with their arms around each other

Touch Her Majesty. Only shake her hand if she offers it. In 2000, John Howard appeared to have put his arm around the Queen, as did US First Lady Michelle Obama in 2009.

Expect the Queen to start the conversation with you if you are sitting on her left during a meal. As etiquette experts Debrett's states, it is customary for the guest of honour to sit to the right of the Queen and the convention is that she speaks to this person during the first course of the dinner, then switches attention to the person on her left for the following course. Formula 1 star Lewis Hamilton, who was sat to her left at one function, didn't know this and tried to speak to Her Majesty but was politely told: "No, you speak that way first and I'll speak this way and then I'll come back to you."

Image caption Actor Tom Hiddleston gave the Duchess of Cornwall friendly shoulder squeeze when they met during a Radio 2 broadcast last year

Leave before the Queen. Debrett's states guests should never leave an event before the royal personage unless permission has been granted through a private secretary.

Turn your back on Her Majesty - it is considered rude.

Take pictures when you are visiting her at home. She may be one of the most photographed women in the world, but unofficial photography is not permitted in royal palaces. In 2015, guests in Germany were advised not to take selfies.

Ask personal questions. Small-talk should be as far as you go.

Get carried away. You may be nervous, but alcohol is not your friend as Debrett's reminds guests in times of "overexcitement or nervousness".

These rules aren't steadfast and those in breach need not fear exile. The official website for the British Monarchy states "there are no obligatory codes of behaviour when meeting the Queen or a member of the Royal Family". It hastens to add: "Many people wish to observe the traditional forms." The choice is yours.