The future of Kylian Mbappe has become this summer's headline transfer saga.

Step forward Saudi Arabian side Al-Hilal, who shocked the footballing world on Monday with an eye-watering world record bid of £259m for the France captain and PSG's record goalscorer.

But what happens now? Could he actually swap the Champions League for the Saudi Pro League? And where is the striker likely to end up?

How have we got here?

Mbappe, who joined PSG in 2017, initially on loan from Monaco before a 180m euro (£166m) move, has scored 212 goals in 260 games.

Despite plenty of domestic success and creating a strikeforce of three of the world's biggest stars in Mbappe, Neymar and Lionel Messi, the Qatari-owned club have failed to achieve their ultimate goal of winning the Champions League.

Mbappe has a contract until June 2024, but last month it was revealed he had told the club he will stay this season but will not extend his deal.

The fallout has become bitter, with PSG leaving him out of their pre-season tour to Japan.

PSG chairman Nasser Al-Khelaifi has made clear his determination to take a tough stance and there have been suggestions Mbappe will not be selected for an entire year if he refuses to break the current deadlock. 

The French club have now given Al-Hilal, one of four clubs owned by Saudi Arabia's Public Investment Fund, permission to speak to Mbappe.

So is Mbappe going to Saudi?

French football journalist Lisa Leroux believes the £259m offer proves Mbappe "really is a once in a generation player" but "he won't go, for him it's more than just about the money".

"No player has ever been offered this salary in football, and I think even in sporting history for one year," she said. "The salary that he would be getting would just be historic and out of this world."

French football expert Julien Laurens agrees and says Mbappe will not go to Saudi.

"He doesn't want to go there" Laurens told BBC Radio 5 Live. "When PSG say we have given permission to speak to Mbappe, he doesn't want to speak to them, Al-Hilal know that. It's not about money for him.

"He just wants to win every trophy possible. Right now, at 24 years old, that does not include the Saudi League."

If not Saudi then where?

Real Madrid are long-term admirers of the player and he was close to a move to Spain before signing his latest PSG deal last year. He says reports he wants to join Real this summer are "lies".

Chelsea, Manchester United, Tottenham, Inter Milan and Barcelona have also expressed an interest.

PSG are open to the idea of Mbappe leaving on loan this summer to see out the final year of his contract elsewhere.

This would allow him to join Real for nothing in 12 months' time, keep playing this season and generate a loan fee for PSG.

"We know for example Barcelona yesterday picked up the phone to PSG, and said listen 'we can't afford any transfer fee for him, we can't even afford his wages',"said Laurens.

"Mbappe earns 72m euros gross a year, but no-one can pay that so he will have to take a pay cut and he's aware of it, but Barcelona said 'how about we swap players for Mbappe, who do you want in our squad?'

"Every big club in Europe is going to try to put something together to maybe, firstly, convince PSG to sell to them, and then convince Mbappe to come to them.

"That could be from United, to Liverpool, all the English clubs, maybe in Italy as well, but Real Madrid are the favourites because they have the money, that's where he wants to go, and they want him.

"As we've been saying before, they've been chasing him since he was 11 years old. Real are the big favourites but are they ready to pay the 150m euros that PSG would want, instead of waiting and getting him or nothing in 12 months' time?"

Is Real Madrid a done deal then?

Laurens thinks Real should move for Mbappe this summer, rather than take the risk of waiting until he becomes a free agent, when they will "get into a bidding war, in terms of signing on fees and wages".

"If they sign him now then their team gets much better already. Why wait if they have the money?" he added.

"Even as a free agent, to sign him you have to give a big signing on fee. For Real it makes sense if they can move now. It is just a matter of when the negotiations start between the two clubs, they are huge favourites to land him this summer.

"They had the money for him a year ago, when he decided, against all odds and as a big surprise, to stay in Paris for longer and not go to Real on a free.

"Even after spending 103m euros on [England midfielder] Jude Bellingham there is space in the wage bill and money available for a transfer fee. If they pay £150m it would be spread over the length of the contract."

Does financial fair play apply to Saudi?

In June, four of the country's leading clubs Al-Ittihad, Al-Nassr, Al-Hilal and Al-Ahli, were taken over by the country's Public Investment Fund, which also owns Newcastle United.

Since the marquee signing of Portugal forward Cristiano Ronaldo from Manchester United in December, the league's 18 teams have gone on a spending spree attracting some of the game's biggest names from across Europe including Karim Benzema, N'Golo Kante and Ruben Neves, while Liverpool captain Jordan Henderson has been linked with a move.

European football clubs have to adhere to financial regulations known as Financial Fair Play, to ensure clubs are not spending more than they earn.

But this does not apply to Saudi Arabia, who play in the Asian Football Confederation, says football finance expert Kieran Maguire.

"What distinguishes the Saudi Pro League from European football is there isn't the restrictions of financial fair play," he said.

"Therefore, even if Premier League clubs do offer more money, they will always be out-bid as they [the Saudi clubs] don't have any cost control restrictions."