Though the pair experienced a difficult – to put it mildly - season at McLaren in 2007, the 'bad blood' between the pair resulting in the exposing of the infamous Spygate scandal which was to cost McLaren $100m and badly damage its reputation, since then a mutual respect has clearly grown.
Though Alonso never added to his tally of two titles, Hamilton has claimed three and looks set to go on to take a fourth in the coming months.
Ironically, while the Briton made a controversial move to Mercedes in 2013 that was to prove the making of the man, the Spaniard now finds himself back at McLaren as it endures one of the most difficult periods in its long history.
Though there is clearly light at the end of the tunnel, Alonso's six points for seventh on Sunday helping his team leapfrog Toro Rosso to take sixth in the standings, there is no doubting the Spaniard's frustration.
While he rarely criticises his team these days, at least publicly, he has made no secret of the fact that he is growing disillusioned with the sport and has admitted that if the new regulations for 2017 do not produce the wow factor that first attracted him to F1 he will walk away, having made no secret of the fact that he is eyeing WEC.
Asked about the possibility in Belgium, Alonso said: "Next year I finish my contract with McLaren, the one that I have now, so I will have to make a decision if I continue in Formula One or not.
"The last couple of years, especially with this turbo engine era, the car is a little bit different to drive," he continued. "I don't say that it's better or worse, everyone will have his opinion.
"But I've been lucky enough to drive 2003 cars, 2004, 2005, even until 2009 the cars were, in my opinion, more extreme, more Formula One cars, so now when I see GP2 running three seconds away, or something like that in FP1 it feels a little bit sad.
"The cars are heavy. No grip. We save fuel, we save tyres, we save everything from lap one, so it's a little bit against the instinct of the driver and next year is a big question mark. I think with the new regs everything will change a little bit. I think if the cars are fun to drive, are exciting to drive, I will probably stay longer and I will drive for more years in Formula One.
"But if the cars are still giving me the feeling that I have in the last couple of years, probably I will stop.
"It's not related to whether you are competitive or not," he insisted. "If you are out in Q1 or winning a championship. It's just you are enjoying driving the cars or you are not enjoying. Right now, in my opinion, the cars are not enjoyable. Probably because I drove other cars. If you arrive now to Formula One, these cars are very fast and very fun to drive... but not for me anymore."
Asked by Spain's AS newspaper if he believes the threat is real and that Alonso could walk away, Hamilton was under no illusion.
"Of course it is. He's 35 and he's already earned enough money. He has won enough races, he has enough experience and he doesn't need Formula One to be someone anymore.
"If he quit next year and I couldn't race against him again, that would be a shame, a real shame," he added. "It wouldn't be good for this sport and it would send out the wrong message. Formula One would not be the same if Alonso didn't continue.
"I still think he is one of the best drivers around, I've always said that, I really hope McLaren can make him a car that would allow him to win again, and so I can compete against him again."