Promoter Eddie Hearn keen for Amir Khan and Kell Brook bout at the Wembley in June

By Kevin Mitchell in London/The GuardianEddie Hearn on Friday handed Amir Khan and Kell Brook the ultimate incentive to bring one of British boxing’s most frustrating rivalries to a dramatic conclusion: a Wembley date in high summer.“I’ve booked Wembley for June 4,” Brook’s promoter said, “which doesn’t mean it’s nailed on to happen, but I think it makes perfect sense for both of them.”Sky Sport’s head of boxing, Adam Smith, said: “They are closer to agreeing terms than ever before.” Given he said that three years ago as well, there will be a lot of fingers crossed over the next few weeks.If the fight does happen, it might not rival the Wembley showdown between Carl Froch and George Groves in front of 80,000 people in 2014, but it will be big. However, both surely realise they cannot drag out the negotiations much longer. The fight was first mooted in October 2012, when Brook had sidestepped an offer from Timothy Bradley and Khan was contemplating a move up to welterweight.Weight is still an issue, however. Brook, who holds the IBF welterweight title, is big at the weight and more than likely will have to move up to light-middleweight towards the end of 2016. The window for a 10st 7lb fight between the two best at the weight in this country will not be open for ever.Khan fuelled the latest speculation when he revealed on Thursday that his preferred opponent, Manny Pacquiao, had declined his offer to share a ring in his farewell in April, and instead had opted to fight Bradley. He might have known disappointment was in the wind, having earlier signed a letter of agreement to negotiate that Bob Arum, Pacquiao’s promoter, had angrily dismissed out of hand. Arum, it seems, has recognised either the danger that Khan’s speed poses or is just doing what he would regard as sensible business by keeping the Pacquiao fight in-house.Nothing is simple in Khan’s career, however. Two factors beyond his control might yet scupper a Brook fight: Ramadan and the International Boxing Federation.The Bolton fighter says they have to meet before the Muslim month of fasting starts on June 6—which makes the June 4 deadline a tight one.The IBF have mandated that Brook must next fight the 31-year-old Canadian Kevin Bizier, which would be a bust in the UK, and would probably be held in Quebec or, says Hearn, New York.In the latter part of Khan’s career, big fights have fallen through or happened way after their best sell-by date, with Floyd Mayweather his chief tormentor, having twice reneged on nod-and-a-wink agreements. Mayweather announced his retirement after beating Pacquiao in one of the sport’s great let-downs, and Khan could only rue his decision not to fight Devon Alexander the first time he had the chance, which might have cemented a challenge against Mayweather, instead of watching Marcos Maidana step in—twice.If circumstances might now finally direct Khan towards a fight with Brook, British fans will be the winners—if Brook gets the moderate Bizier out of the way early enough. Brook has been resting a rib injury that interrupted his programme this summer after two low-key stoppage defences of his title, against Jo-Jo Dan and Frankie Gavin. Dan, not one of the best world title challengers to reach these shores, lost twice on Bizier.