They have been this way before, of course, presiding over two Premiership Grand Finals and one European Cup for Wasps. Not only are they on familiar territory but the happiest of hunting grounds to boot for two men born 12,000 miles apart in the Sixties.
One has come from the other side of the world, from the farmlands of the Waikato; the other from an old Lancashire mill town famous for George Formby, its pier and its pies - Wigan.
Each has crossed a landmark along the way, Gatland from the far side of the Equator, Edwards from the far side of the Rubicon that used to divide Union from League.
Before he had finished winning everything there was to win in League many times over, the coalminer's son had found time to conquer Twickenham as well, with the galactic Wigan team at the Middlesex Sevens in 1996.
In tandem as coaches, Gatland and Edwards are used to seeing their teams win often against the odds as Wasps did against a superior Toulouse when a dithering Clement Poitrenaud waited too long for the ball to bounce in-goal and another of the new Welsh coaches, Rob Howley, stole the winning try.
Back at 'Headquarters' the following year, the Gatland-Edwards combination upset another party, the one that was supposed to have sent Martin Johnson off into retirement reunited with the Premiership trophy at the end of his last match for Leicester.
Instead Wasps turned it into one of the most anti-climactic occasions the Tigers have ever had to endure.
Now the new Wales head coach and the new defence coach are back on a brief inspection of the premises.
What awaits them is something neither has experienced before: England versus Wales, an event perceived by many from the far side of Offa's Dyke as rather more than a rugby match, a chance to give big brother a bloody nose.
Despite finishing bottom of the RBS 6 Nations pile the previous season, despite their ignominiously early exit from the World Cup a few months earlier, the western neighbours are out in force as usual.
This is the one match Wales does not forgive its team for losing. Gatland will have sensed that expectation and perhaps that is why, standing on the edge of the pitch, he hopes for the best but gives an impression of fearing the worst.
Looking around at the vast emptiness of the triple-tiered stands steepling above him, he confesses to being 'a bit twitchy, nervous and pretty apprehensive.'
For Gatland, the fixture marking his return to international coaching seven years after the controversial end to his stint with Ireland is an ideal one. Wales are not expected to win and Twickenham, as he points out has been 'a great hunting ground.'
Fortune-tellers being very thin on the ground that Friday, the idea that this would be the first step towards a Welsh Grand Slam is too far-fetched for anyone to mention.
England might have fallen some way off their global pedestal of 2003 but they had still managed, by hook or by crook, to reach the World Cup final the previous October.
In doing so they became the first country to achieve the strangest of doubles, losing twice to the same opponents in the same tournament - 36-0 to South Africa in the pool competition at the Stade de France and 15-6 at the same venue in the final five weeks later.
When the first day of his Welsh reign dawned, no amount of pre-match twitchiness had prepared Gatland for an opening 40 minutes when England ought to have put Ryan Jones' team out of their misery.
They would have done had the TMO not denied Paul Sackey a try in the corner just before half-time when England thought they had increased their lead to 15 points with a conversion to come.
"We should have been out of the game by half-time," Gatland said in the euphoric aftermath of a 26-19 away win, thereby ending a run of nine straight England home wins over Wales since 1988. "I thought we were really poor in the first half."
England, hamstrung by injuries to flankers Lewis Moody and his replacement, the unlucky Tom Rees, had no option but to use their World Cup winning lock, Ben Kay, in the back row.
It hardly helped their mood to learn that Wales may have been given some divine assistance.
The match marked the anniversary of the death of Edwards' 21-year-old brother Billy-Joe in a road accident four years earlier.
Their mother, Phyllis, had visited the grave that Saturday, leaving home at the end of the first half when Wales were 16-6 adrift.
"I rang her after the match and she was shaking," Edwards said. "She went to the cemetery to pray and by the time she left, we'd won…."
A few weeks later, Wales had won the most unexpected of Slams. They won another two years ago on the strength of their most recent Twickenham smash-and-grab, as secured by Scott Williams' solo try.
This time they are both playing for a shot at the title on the final round next week, England in Rome against Italy, Wales in Cardiff against Scotland.
England, who have never failed to win at Twickenham in a Triple Crown decider, will view the prospect as some retribution for their hammering in Cardiff 12 months ago.
Should England's improving young team repay Wales in full for last season's heavy defeat, the consequent increase in their points-difference would put them in a position to win the title. They won't be lacking in the motivational department.
As flanker Tom Wood said earlier in the week: "We want to take the lessons and the hurt from that game and allow it to fuel our preparations."
For the record, how they lined up at Twickenham for the first Gatland-Edwards Test, February 2, 2008:
England 19 Wales 26
England: I Balshaw; P Sackey, M Tindall, T Flood, D Strettle; J Wilkinson, A Gomarsall; A Sheridan, M Regan, P Vickery, capt; S Shaw, S Borthwick; J Haskell, L Moody, L Narraway.
Subs: L Vainikolo for Strettle, T Rees for Moody, B Kay for Rees, L Mears for Regan, D Cipriani for Tindall, M Stevens for Vickery.
Try-T Flood. Conversion-J Wilkinson. Penalties-J Wilkinson 3. Drop goal-J Wilkinson.
Wales: L Byrne; M Jones, S Parker, G Henson, S Williams; J Hook, M Phillips; A Jones, H Bennett, D Jones; A-W Jones, I Gough; J Thomas, M Williams, R Jones, capt.
Subs: A Popham for J Thomas, T Shanklin for Parker, G Jenkins for A Jones, M Rees for Bennett, I Evans for A-W Jones.
Tries-L Byrne, M Phillips. Conversions-J Hook 2. Penalties-J Hook 4.
Round Four of the four-horse race for the title opens in Dublin and appropriately so on what will be a historic occasion.
On his final international appearance in his home city, Brian O'Driscoll will become the most-capped player of all-time, his 140th Test eclipsing the total set by George Gregan.
The Australian scrum-half has held the distinction since overtaking Jason Leonard's total eight seasons ago.
That O'Driscoll is now about to take it to stratospheric new levels is a wonderful tribute to the finest European threequarter the professional game has seen.
England, Wales and France will probably disagree because of an obvious conflict of interest but how fitting it would be for the evergreen Irish Lion to leave the stage with the RBS 6 Nations trophy in his hands. Rugby, as we have seen so often, doesn't really do fairytales.
"It's been good," O'Driscoll said of his marathon career with typical modesty. "Leaving something you have done all your adult life will be hard.
"One day you are part of it, the next day you're not. I'd enjoy it a lot more if we're walking round the Stade de France with a trophy…'
For there to be any chance of that, Ireland must see Italy off. Scotland, with Kelly Brown restored to the captaincy, return to Murrayfield against a France team shaken by their fall from grace in Cardiff.
Their travel sickness is such that Edinburgh remains the only place where they have won on the road in eight away championship matches.