To wait amidst thousands of others for the arrival of tonight’s headliners is to enjoy sharing in a type of anticipation that just doesn’t happen at any other kind of gig, because there really aren’t any other gigs like this. The only thing I can compare it to is when I saw David Beckham play for Manchester United many moons ago. Such a huge celebrity that his off field exploits were being reported in the national press far more widely than his match day efforts, to see the actual David Beckham stood there, kicking a ball, kicking other people and having other people kick him back, was nothing short of bizarre. I remember the crowd’s playful, gently goading enquiries about Posh Spice were like water off a ducks back to the guy: They may as well have been mocking a fictional character.

Jay-Z and Kanye West are at an even higher level of celebrity. This is one man who recently fathered Beyonce’s child, and another who the President of the United States has a personal nickname for (the nickname might be “Jackass”, but it’s closer than I’m ever going to get). The pair might know who Beckham is, but he’s sure as hell heard of them. They are at once everywhere, their ubiquitous presence making them seem unreal. Yet soon they will appear, here, the both of them, together, and they’re going to do something that, given the level of their public profiles, it’s often easy to forget they do – they’re going to rap! The first of many moments of joy in the evening’s set doesn’t however come from anyone recognising the opening song; it comes from 20,000 people simultaneously experiencing an invigorating mixture of relief and bafflement - “Yes! THEY EXIST!”

After confirming their existential status as best they could, they settle my other worry – how can two characters of such prowess, talent and ego ever possibly share a stage? By having separate podiums, one at either end of The O2 of course is the answer. Slowly but surely, these platforms are elevated toward the ceiling, revealing video screens that display pictures of snarling dogs and presumably angry sharks (sharks are always angry, right?). The footage faces the crowd whilst West and Z tower some 20 feet above them, rapping at each other from opposite ends of the cavernous arena. To use this report’s buzzword for the first time, it is ridiculous, but also hugely enjoyable – you want this to be a spectacle, and from the off it’s clear that is exactly what you’ll get. Though everything tonight is largely done to a backing track, this isn’t without musical merit either – it’s quite the skill to see two men rapping a capella together in perfect rhythm when there’s about half a kilometre between them.

As well as being arguably the two most famous men in rap, Kanye West and Jay-Z are also its best friends. The tangible camaraderie between them means that when they do finally join forces for ‘Otis’ (in front of a huge American flag and pyrotechnics so hot you can feel it from the back seats), any thoughts on one being more famous than the other disappear. Unlike other nights in this run of O2 shows, there are no guest appearances but it doesn’t matter a jot – spending over two and a half hours solely in the company of this coupl’a fellas just reaffirms their prowess. And when they’re not coming across like the best buddies since Bill and Ted, they’re playing a cheeky game of one-upmanship.

Whilst their collaborative effort Watch The Throne is the best album Jay’s been involved with in many a year, the same isn’t true of Kanye, whose My Beautiful Dark Twisted Fantasy just edges it out for the accolade of Biggest, Silliest, Most Important Hip Hop Record of Recent Times (check – there probably is a Grammy for that). Their set list choices reflect the commonly accepted theory that Kanye’s currently on top of his creative game in a way that Jay can’t match. It’s only ‘Empire State Of Mind’ from Hove’s recent material that can really stand up to anything from Yeezy’s career-best, most recent LP. And whilst he’s still the better of the two when it comes to the technicalities of actually rapping, it’s clear that Jay will never compose something quite so epic, so full of ambition as ‘Runaway’, which Kanye delivers solo from atop his now bright red video cube at the back of the venue. It’s a sight to behold, even if it is sung wholly in auto tune.

The times when they attempt to be thought provoking do work, but perhaps provoke the wrong thoughts. I’m not sure how they expect dedicating ‘No Church In The Wild’ “to London for the riots” to go down, but lines like “coke on her black skin made a stripe like a zebra” certainly don’t have many pondering the lack of inner city social mobility or the death of Mark Duggan. When they turn their backs to the crowd and stand motionless watching on-screen images of Molotov cocktails being thrown at police and Klu Klux Klan members sinisterly pulling hoods over the faces of their children, it’s difficult to know what Jay and Kanye are mulling over either. Perhaps it is how many times they’re going to play a closing song called ‘Niggas In Paris’ to an audience of (largely but certainly not wholly) well-off white folks who’ve paid £70 each for a ticket? The answer’s five times, by the way.

It’s no surprise to find the set is best when it’s at its most ridiculous; the way the two try to thread together their solo material with so-bad-it’s-funny banter sees every hit they’ve ever had recast as some timely commentary on each other’s relative successes and failures with the opposite sex. What else can Jay do after Kanye’s blown the roof off’a the place with ‘Golddigger’ than return to the stage with a jovial reply of “You havin’ girl problems, Ye..? If you havin’ girl problems I feel bad for you son…!” Cue an eruption. It’s also oddly pleasing to see that talk of him retiring the word ‘bitch’ from his lyrics after the birth of his daughter was wide of the mark, if only for the fact that hearing Jay-Z tell us of how he has “99 problems but ah, y’know, I just don’t wanna talk about it” simply wouldn’t have the same impact.

I’m not even sure on what level exactly, but a Watch The Throne gig certainly does make an impact. It has the curious effect of making the ones on the Throne seem more like real people than ever, and also like the most surreal people in the world. And in a game so obsessed with “keeping it real”, you really have to salute the lengths they’ve gone to in order to explore what it’s like to do things another way.