Personnel might be part of that.

Jones earned rave reviews in his early England days, with captain Jamie George lauding the "crazy energy" he was coaxing from their defence. But Jones didnt have the endurance to match, handing in his notice after a little over seven months in post.

Joe El-Abd - Englands third defence coach in less than a year - has replaced him, initially splitting his duties between the national side and French second-tier club Oyonnax.

England have stressed that there is a continuity in defensive philosophy, but, even so, a changing cast of coaches wont have helped bed it in.

Then there is the nature of the tactics themselves.

Jones was the mastermind behind South Africas blitz defence, with tacklers rushing up in defence, attempting to shut down opponents time and space.

England have hoped to do the same.

When it works well, the tactic squeezes teams, denying them momentum and creating turnover opportunities. Those are the rewards, but the blitz is also high-risk.

On-rushing defenders are more easily evaded and, moving at pace, the holes they leave behind are hard to plug. A blitz defence can post impressive gainline numbers or contain a team for sustained periods, but, when it fails, the errors can also be more costly. Big territorial losses and heavy scoreboard damage can result.

South Africa centre Andre Esterhuizen says that a successful blitz lives on a knife-edge flipping from ferocious front-foot aggression to desperate corner-flagging cover in the blink of an eye.

"The biggest thing about that system is scramble," he told Rugby Union Weekly earlier this week.

"You are going to make misreads, you are going to make mistakes, but it is how your team-mates around you fix it for you.

"We say that 80% of your reads you are going to get right, but 20% you are going to get wrong and thats where we work hard and scramble for each other."

During his time with England, Jones said that finding that balance is key. He warned that an emphasis on aggression can, at times, tip too far and leave teams vulnerable.

"You have to push yourself to where the margins are so small and you're right on the limit of execution," he said.

England are still trying find that sweet spot and master a tricky tactic. Jacques Nienaber, former South Africa head coach, reckons it took the Springboks 14 matches to get right when he came into their set-up in 2018., external