Tall as well as stocky and weighing in at 110 kilos, when the going gets tough the rugged and abrasive Hartley, with the whites of his eyes fixed on an opponent, is rarely found wanting.
Controlling that aggression, however, has been the hooker's problem throughout a career plagued by disciplinary issues.
The 29-year-old has accumulated a massive 54 weeks in bans, and has missed two World Cups and a British and Irish Lions tour because his fiery temper has repeatedly got the better of him.
That new England coach Eddie Jones is prepared to risk handing the captain's armband to a maverick player with such a short fuse is testament to what the Australian wants to see from his new-look team.
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One of the criticisms of Stuart Lancaster's reign, which ended with a humiliating group stage-exit for the hosts at last year's World Cup, was that England were a little too nice, too rigid and too robotic.
Lancaster, perhaps rightly so, adopted a zero-tolerance approach to ill-discipline after the notorious 2011 World Cup "dwarf-throwing" debacle in a New Zealand bar, demanding his players behave like role models.
The former England coach was quick to swing the axe on Hartley last year after was banned for head-butting an opponent, booting him out of his World Cup training squad.
A contrite Hartley was again left to apologise, telling those still prepared to listen that his "world had fallen in".
RUTHLESS STREAK
Redemption, however, has come in the shape of Jones, a coach with a ruthless streak and an engaging turn of phrase.
Getting Hartley to keep playing on the edge while controlling his emotions will be his number one priority.
"For me missing out on the World Cup... I thought I'd played my last game for England," Hartley said last week after he was selected in Jones's Six Nations squad.
That Hartley, with 66 caps, is England's most experienced player is a measure of the responsibility now resting on his shoulders.
Hartley has proved himself as a leading exponent of the hooker's position, his physicality and set-piece excellence making him an automatic choice for Jones.
While he is not new to captaincy having led Northampton for six years until this season when he relinquished the role, not everyone is convinced of his suitability.
Martin Johnson led England to World Cup glory in 2003 and the burly lock forward, despite being no shrinking violet himself when it came to on-field ill-discipline, is not certain Jones has the right man.
"Would I have an issue? It doesn't matter what I think. There probably is an issue, isn't there?," Johnson, who gave Hartley his debut in 2008 when he was manager of England, said.
Hartley's coach at Northampton, Jim Mallinder, knows better than most and he is in no doubt.
“He leads by example," he said.
“He motivates and inspires the players. He’s not a massive talker, but he really gets the team wanting to play for him."
(Editing by Ed Osmond)
