Manchester United have lit the fuse on what will be the transfer saga of the summer by contacting Liverpool to express interest in signing Raheem Sterling.
The Mersey side club instantly rebuffed the inquiry from Old Trafford, making it clear that they have no wish to sell the 20-year-old and would certainly never do business with United.
It is a daring, if somewhat optimistic move by United and Louis van Gaal. The manager evidently sees Sterling as a player who can enhance his side ahead of a title challenge, but the weight of history is against the Dutchman if he expects Liverpool to open negotiations with their North-West neighbours.
United are understood to have contacted Liverpool in the past week, aware of the contract impasse involving the youngster and wishing to establish how much he would cost. Despite Liverpool's insistence that Sterling is not for sale, United know there is a chance that the England winger will go for a hefty price this summer and that both Manchester City and Chelsea are monitoring developments.
It remains to be seen if United take their interest further and test Liverpool with a formal bid, or whether they were merely assessing the strength of Liverpool's resistance to negotiations
Such a proposal from United was always going to be controversial, not only because Liverpool are determined to block all approaches for Sterling but also because dealing with United would be considered the ultimate betrayal.
Even though Liverpool's hardline stance would relent if a crazy bid were to be made, a deal with United is the most unpalatable possible for Anfield officials. United are the one club in the world to whom they would never sell their best player.
No player has moved directly between the clubs since 1964, when Phil Chisnall went from Old Trafford to Anfield. The last player to go from Anfield straight to United was Allenby Chilton in 1938, and he had not made a senior Liverpool appearance before making the switch.
The historic rivalry between both clubs has polluted all negotiations between them in modern times. High-profile players such as Paul Ince and Michael Owen played for both clubs, but only after going elsewhere in between, and it still wrecked their reputation with the fans who once adored them.
When former Liverpool manager Rafa Benitez tried to sign Argentine defender Gabriel Heinze in 2007, meeting the valuation in his exit clause, United successfully blocked the proposal after a court battle, saying that it was their club policy not to negotiate with Liverpool.
That United feel confident enough to ask about Sterling offers an insight into how tempestuous his eventual exit from Anfield will be, whether it is in a few months, next season or at the end of his contract in 2017.
Sterling has already incurred the wrath of supporters for the manner in which he is seeking a move, but if he is prepared to go from Liverpool to United the jeers he has encountered thus far will sound more like wolf whistles.
United are the first club to make contact with Liverpool since Sterling made his frustrations public, but they are unlikely to be the last.
Manchester City are known to be admirers and have been awaiting the outcome of the meeting between Sterling's agent, Aidy Ward, and Liverpool chief executive Ian Ayre, which is scheduled for Friday.
There are suggestions that City are prepared to open the bidding at pounds 40?million, while paying Sterling pounds 200,000 a week. If that really is the case, it makes a mockery of Sterling's representatives agitating over the past few months.
A pounds 40?million bid would not be enough to sign the player, but it would suggest the pounds 50?million asking price might eventually be met. If that happens a mutually beneficial deal could be agreed, which would have avoided the hostility that has soured Sterling's relationship with Liverpool supporters.
Liverpool doubt any Premier League clubs will match their valuation, and are braced for the dispute to continue, reiterating to Sterling and his representative that he has two years left on his deal and that he will not be sold to a rival.
Sterling earns pounds 35,000 a week on terms that run until 2017. Should he be tied to his contract he could go abroad for a small compensation fee in two years, or have his fee determined by tribunal should he move to another English club.
It is believed that he will ask to leave Liverpool because they failed to qualify for the Champions League and he believes that he will have more chance of winning medals elsewhere.
Earlier this season, Liverpool offered Sterling a pounds 100,000-a-week contract, which was rejected because he was seeking pounds 150,000 a week. Sterling later called off contract talks entirely, arguing that his dispute was "not about money".