Queen Elizabeth’s garden party in the gardens at Buckingham Palace in London on Tuesday would have turned out perfect except for the fact that it rained. Guests had to shelter under umbrellas.

So what happens at a garden party?

Garden parties take place between 4 and 6 p.m., although the palace’s gates are normally open from about 3 p.m. The Queen and The Duke of Edinburgh, accompanied by other members of the Royal Family, enter the garden at 4 p.m., when the national anthem is played by one of the two military bands playing selections of music along the rest of the afternoon.

After the playing of the anthem, The Queen and The Duke of Edinburgh, together with other members of the Royal family, circulate among the guests through “lanes” which are peculiar to Royal garden parties.Each takes a different route and random presentations are made so that everyone has an equal chance of speaking to Her Majesty and members of her family. The Queen and other members of the Royal family eventually arrive at the Royal tea tent, where they meet further guests.

In both London and Edinburgh there are tea tents for other guests. Tea and other refreshments are served from long buffet tables. The quantities served are enormous.

At a typical garden party, around 27,000 cups of tea, 20,000 sandwiches and 20,000 slices of cake are consumed.

Some 400 waiting staff are involved in the serving.

At about 6 p.m., the Queen and other members of the Royal family leave the garden, when the anthem is played once again to mark the end of the party.