After months of planning it's finally here - the world's biggest music event kicks off in Liverpool later with the first semi-final of the Eurovision Song Contest.

Fifteen countries will compete for 10 places in Saturday night's grand final.

Tuesday night's show, hosted by Alesha Dixon, Hannah Waddingham and Ukrainian singer Julia Sanina, will be broadcast live on BBC One from 20:00 BST.

It will be down to viewers to decide whose choreography was on point, who could hit the high whistle notes, and which costume caught the eye.

The second semi-final takes place at the Liverpool M&S Bank Arena on Thursday.

Ukraine qualify for the final after Kalush Orchestra won last year. France, Spain, Germany, Italy and the UK are also through because they pay more to organisers, the EBU.

What to look out for

Some of the biggest hitters in the competition perform tonight, including two of the favourites to win the whole contest - Finland and Sweden.

With it generally being considered the stronger of the two preliminary stages this year, there is a real risk of a shock elimination.

There's a lot of talk about Swedish act Loreen this year, the bookies' favourite. She won in 2012 with her track Euphoria and wants to become the first woman to win twice. This time she's singing Tattoo.

Also looking for a spot in the final is Finnish rapper Käärijä, who says he views her as his main competition - could they set up a battle of the Nordic nations for the final?

But it's Let 3 from Croatia who will no doubt have viewers staring at the screen wide-eyed, when the band strip down to their underwear as missile props join them on stage.

For slick dance moves, strong vocals, and a new word, "femininal" stay tuned for Israel's Noa Kirel and her track, Unicorn.

Songs on a royal theme

Three days after the coronation of King Charles and Queen Camilla, Norway will open tonight's show with a royal themed, up-tempo banger, Queen of Kings, performed by Alessandra.

How does the semi-final work?

The show starts at 20:00 BST and, after all 15 acts perform, voting lines open.

In a change to the rules this year, the decision rests entirely with the public. Votes from the national juries only come into play for Saturday's final.

Semi-final one running order: 1 Norway; 2 Malta; 3 Serbia; 4 Latvia; 5 Portugal; 6 Ireland; 7 Croatia; 8 Switzerland; 9 Israel; 10 Moldova; 11 Sweden; 12 Azerbaijan; 13 Czechia; 14 Netherlands; 15 Finland

But viewers in the UK will not be able to vote in Tuesday's semi-final. They will have to wait until the second semi-final on Thursday to have their say.

This year a "rest of the world" vote has been introduced so countries not participating can have their say. Those votes will be added up to come from one extra country. And added to those from participating countries.

The results are delivered in a different way to the final - there is no bounce around Europe for votes. The acts are simply told who is going through.

Ukraine's party, at the UK's house

When the BBC confirmed it would host Eurovision on behalf of Ukraine, because of Russia's invasion, last year's UK contestant Sam Ryder said it would be Ukraine's party in the UK's house.

That theme runs throughout tonight's show, including an interval performance from Liverpudlian Rebecca Ferguson. She duets with Ukraine's 2010 entrant Alyosha who fled her country last year when Russia invaded.

The LED screens behind their powerful take on Duran Duran's Ordinary World will light up with text messages from Ukrainian refugees to friends and family back home.

The slogan for this year's competition is United by Music and tonight there will be something to suit everyone's taste.

What you won't see on TV

What the cameras won't capture tonight are the talented stage technicians who have choreographed in a month how to change the stage setup between performances in less than 60 seconds.

At the first rehearsal in a packed arena last night, not only could you feel the buzz in the arena, you could feel how the silent crowd were in awe of what was happening.

As well as three televised shows, fans have been able to get tickets for six rehearsals, with tickets set aside for Ukrainians living in the UK. Their flags waved proudly.

It's the first time two countries have jointly hosted Eurovision, and if show one is anything to go by, we're in for a gripping week. (BBC)