According to the Collins English Dictionary, the sword of Damocles is an idiom that describes someone "in a situation in which something very bad could happen to them at any time". Paul Gustard jokes that he knows the feeling well -- it is one that will return when he watches England play Scotland alongside Eddie Jones from the coaching box at Murrayfield this Saturday.
Gustard, the defensive guru who has helped mould England into one of world rugby's least hospitable teams should be preparing for the Calcutta Cup clash in confident mood.
His side turned in one of the best defensive displays of the Jones era as they kept Wales try-less during a 12-6 victory at Twickenham 10 days ago. Gustard labelled that stand "outstanding" last week, but he is well aware that it will count for little if they are unable to replicate it this weekend.
"I am sat three feet away from Eddie Jones. The tension never goes," Gustard said when asked if there would be any anxiety in the stands in Edinburgh. "It is the sword of Damocles hanging over my head!
"I reckon in the first five minutes, [it is about] how do you attack first? How does someone carry the ball into contact? How aggressively do we clear out their tackle threat? How hard do we hit that first tackle? How fast is our kick-chase? How hard is that maul, etc, etc.
"You can kind of gauge whether our preparation has been right in that first contact."
That initial act has not always gone according to plan for Gustard and England.
Jones has presided over 24 victories in 25 matches as England boss but his defence coach admitted that he got things wrong ahead of the first Test in Australia in June, 2016 -- a game in which they conceded two tries in the opening 16 minutes before recovering to win 39-28.
"He [Jones] makes it clear," Gustard added. "There have only been a couple of games where things have not been right. The first Test in Australia in 2016, I look at our preparation, I got things wrong.
"I know there were individuals where things did not go quite right for them, but ultimately it was my fault as I prepared the team wrongly.
"When the look came across [from Jones] I realised."
That experience in Brisbane has shaped the way that Gustard approaches his work with England. Instead of focusing on the perceived strengths and weaknesses of Gregor Townsend's Scotland, he will concentrate on making his defence as strong as it can be.
It is up to Townsend and his coaches to figure out a way to break them down. Not the other way around.
"We have belief in our defence like we have belief in our attack, that we can cause teams problems," Gustard said. "We have enough firepower in our team in terms of attacking strengths. We've got good collective unity in terms of our defence. We've got very strong set-piece.
"We are well equipped to take on any team in the world and get the result we want."
Gustard will be a vocal presence at England training in Surrey this week. He sees it as his job to give the players the emotional energy to go out and perform at the required intensity on the weekend.
"Rugby is not just tactical or technical, there is an emotional side that you cannot divorce from the tactical side," he said. "All the time you are trying to feed them emotionally, and feed them that desire to defend."
His end goal is to produce a defence capable of helping England win the Rugby World Cup in Japan in two years' time.
Neither he nor Eddie Jones -- nor any of those currently involved with England -- will be satisfied until they are hoisting the Webb Ellis Cup aloft in Yokohama on Nov. 2, 2019.
Gustard added: "We are not going to be happy until we beat Scotland, we will not be fully happy until we win the Six Nations and we will not be entirely happy until we win the World Cup.
"For all those steps along the way, we will have to keep improving all facets of our game. It was a good defensive performance against Wales, they tested us at times.
"The need is for us to continually strive for excellence and that is my job, that is what I am paid to do."