It is one thing to say that there is no English hooker quite like Dylan Hartley – the exiled New Zealander is unique in his approach to the darkest and most demanding position on the field, temperamentally as well as technically – and quite another to suggest that there are no other English hookers worth a light. But Hartley's latest injury has sent the red-rose hierarchy into a tailspin: if, as many expect, the scan on his damaged knee rules him out of the forthcoming autumn international series against the might of the southern hemisphere, it will be just about the worst possible news for Stuart Lancaster and his fellow coaches.
As recently as last year's World Cup in All Black country, the hooking role was the least of England's worries. Steve Thompson, a Webb Ellis Trophy winner in 2003, and Lee Mears, a Lions Test front-rower against the Springboks in 2009, were in the party alongside Hartley.
Since that time, Mears has retired from international rugby and the even longer-serving Thompson has packed it in altogether. Their departures have exposed a weak point in the red-rose armoury.
Hartley's official understudy for the imminent meetings with Fiji, Australia, South Africa and New Zealand is the uncapped converted centre Tom Youngs – a player rich in potential but struggling badly in at least one crucial discipline: line-out marksmanship.
When Hartley, recently sidelined with a fractured eye socket, suffered his knee problem while leading Northampton against Saracens at Franklin's Gardens three days ago, England called up the Australian-born David Paice of London Irish, who has not featured in red-rose plans since the calamitous trip to New Zealand in 2008.
Paice is not the sort of man to let a team down: at the age of 28 he has been around the block more than once, picking up many a bruise and learning many a hard lesson along the way. As Brian Smith, the former England attack coach who now runs London Irish, pointed out: "He has a quality set-piece game and as he's not young, he's not likely to choke on his chance."
But the fact remains that the Exiles forward was a long way down the pecking order when the national squad was first pieced together back in the summer. Not only were Hartley and Youngs ahead of him; he was behind Rob Webber of Bath and Joe Gray of Harlequins too.
Webber and Gray are both injured at present, but neither are in Hartley's class anyway. So given England's grand tradition in this area, stretching back to the revered Lions forward John Pullin and beyond, it is legitimate to ask: where have all the hookers gone?
Numerically speaking, there is not an obvious problem. In last weekend's round of Premiership matches, nine of the starting No 2s were England-qualified. But one of those was Mears, who is no longer available to Lancaster, and another, Tommy Taylor of Sale, has only just broken into senior rugby. The rest are either works in early stages of progress – Rob Buchanan of Harlequins and Tom Lindsay of Wasps fall into this category – or honest-to-goodness journeymen.
One club, Saracens, has hooking quality oozing from every pore: Jamie George and Scott Spurling, both of them England age-group forwards, are widely considered to be brilliant prospects.
The South African maestro Schalk Brits, perhaps the most lavishly gifted footballing hooker in the world game, certainly shares that opinion. "Outstanding talents, both of them," he told this newspaper back in the spring. "Far from being overrated, I think they're underrated. I'm not a gambling man, but I have a bet with someone that Jamie will play at the next World Cup."
The problem? Neither George nor Spurling see much first-team rugby. Why? Because Brits keeps them out of the side.
As things stand, Hartley is close to irreplaceable. The only other player that England cannot afford to lose is Dan Cole, the Leicester prop, although David Wilson of Bath at least has some meaningful international experience in the bank. Alarmingly, tight-head specialists are in even shorter supply than hookers – of the No 3s who started for their clubs at the weekend, half were either foreign or in Test retirement.
Meanwhile, the Springboks are heading this way with Brits in their party. As for the All Blacks, they are travelling at something close to full strength, with the two greats of this silver-ferned era, the outside-half Daniel Carter and the flanker Richie McCaw, among their number.
Needless to say, they are not in the throes of a hooking crisis: the World Cup winners Keven Mealamu and Andrew Hore are safely on board, along with the highly-regarded newcomer Dane Coles.
Steve Hansen, the head coach of New Zealand, believes that the Wellington rookie is "more than capable of stepping up". Dane Coles against Dan Cole in the front row at Twickenham on Saturday 1 December? It could happen.