England defence coach Felix Jones has become the latest key figure to quit Steve Borthwick’s set-up.
It comes after strength and conditioning guru Aled Walters left to join Ireland.
It is understood Jones has a 12-month notice period in his Rugby Football Union contract.
But it is believed he has handed in his resignation after just seven months in the role.
The 37-year-old joined England’s coaching set-up after last autumn’s World Cup, having helped South Africa become back-to-back world champions.
The Rugby Football Union is not commenting on Jones’ situation, but his decision will come as a major setback, especially in the wake of Walters’ departure.
The pair worked together at Munster and South Africa and are known to be very close.
Former Ireland international Jones, 37, has forged a remarkable coaching career to date having won two Rugby World Cups with the Springboks, in 2019 and 2023.
Since replacing Kevin Sinfield as defence coach in January, Jones has been responsible for revolutionising England’s approach without the ball by introducing an aggressive blitz defence, and was considered a vital part of the coaching ticket going forward.
Meanwhile, Sinfield’s position is uncertain after he originally announced his intention to leave this summer, just 18-months into a five-year contract.
However, Borthwick confirmed following the recent tour of New Zealand that Sinfield is expected to stay as a part-time skills coach.
Even though Jones is thought to be under contract for the next year, Borthwick will now be on the look out for a new defence coach.
The England boss also has to recruit a whole new strength and conditioning department after Walters and Tom Tombleson both left their roles this month.