Ange Postecoglou says he would not want his Tottenham players to engage in the game’s darker arts on set pieces as Ben White did for Arsenal in ­Sunday’s north London derby. White was assigned to distract the Spurs goalkeeper, Guglielmo Vicario, taking a starting position behind him on corners and, just before the kick was taken, moving around, backing in and blocking him from reaching the ball.

The Arsenal defender performed the trick on both of his team’s first-half corners – no Spurs player was close to him – and each resulted in a goal: the first a Pierre-Emile Højbjerg own goal for 1-0, the second a Kai Havertz header for a 3-0 half-time lead. Before the first corner, White had grabbed at the cuff of one of Vicario’s gloves. None of his actions drew a whistle from the referee, Michael Oliver.

Related: ‘More mature’: Spurs admit Arsenal’s mentality made the difference in derby

Spurs’ problems when defending set pieces have been increasingly clear. They have conceded from 14 of them in the Premier League this season (excluding penalties) – the joint-fifth worst record in the ­division – and let in six goals from corners in their past nine games.

It was noticeable that ­Postecoglou, who takes his team to Chelsea for another London derby on Thursday night, gave the half-time substitute Pape Sarr a man-marking job against White on each of Arsenal’s four second-half corners. Sarr tracked White step-for-step, matched him physically and did not allow him to get at Vicario.

Arsenal did not capitalise further, although Postecoglou’s intervention appeared to be too little, too late. Arsenal ran out 3-2 winners. The Spurs manager has his principles and he indicated they did not include White-style blocking on set pieces.

The former Tottenham and Wales winger Terry Medwin has died at the age of 91. Medwin won 30 caps and was part of Spurs' 1960-61 Double-winning side and victorious 1962 FA Cup team.

"The club is deeply saddened to learn of the passing of our former player, Terry Medwin," Tottenham said on X. "Terry was part of our double-winning side in 1961 and made 215 appearances in all competitions, scoring 72 goals. Our thoughts are with Terry's family and friends at this impossibly sad time."

The Swansea-born Medwin began his career at his hometown club and made his Wales debut in 1953. He scored 57 goals in 147 league appearances for Swansea before joining Spurs for £25,000 in May 1956.

He played at the 1958 World Cup in Sweden when Wales reached the quarter-finals before losing to the eventual winners, Brazil. Medwin's winner in the 2-1 victory over Hungary was Wales' last goal at a World Cup until 2022.

He managed Cheshunt and coached at Cardiff, Fulham and Norwich before returning to Swansea as John Toshack's assistant, where he helped them rise through the leagues in the late 1970s and 1980s. PA Media

“It’s a strategy,” Postecoglou said, when asked whether the moves were cheating or dark arts. “You can label it but it’s a strategy. I’m not casting judgment. If people are going to think that’s going to give them an ­advantage or whatever … I don’t worry about that stuff. I just try to focus on building teams that win things.

“If it’s not going to be that then it’s going to be something else. I know it’s great theatre. Whether he [White] is trying to undo his glove, tickle his armpit or whatever … I don’t care. I try to get my players not to focus on that stuff.

“If you want to go down that ­avenue … what’s he [Vicario] ­supposed to do? Throw a punch and knock him out? Or say: ‘Please don’t touch me?’ What does that do? ­Seriously, we’re not in the schoolyard. To be honest, if I saw one of my players do it, I’d be saying: ‘Mate, seriously? Get the ball and play some football.’”

There was an irony to Vicario’s actions in the final minute of stoppage time when Spurs won a corner. He went forward and stood next to the Arsenal goalkeeper, David Raya, jostling with him. Pedro Porro’s delivery was poor and Arsenal cleared.

Postecoglou admitted he was bemused as to what constitutes a foul on the goalkeeper and revealed that Spurs had contacted the referees’ body in England to ask for clarity.

“I watched the Champions League tie between Bayern Munich and Real Madrid [on Tuesday] and there was a couple of times they went in on the keeper and it was a foul straight away,” Postecoglou said. “It is a weird one for me.

“You’re allowed to reach out [to the referees’ body]. We just wanted some clarity on what the actual position is on interference on the keeper. I’m ancient and I always thought that the keeper was a bit of a protected species. Maybe that’s shifted now and I missed the memo. Did I get clarity? No, not really.”

Postecoglou, who reported that Ben Davies and Timo Werner had sustained muscle injuries against ­Arsenal to end their seasons, is adamant that his team are on the right path. They have 60 points with a tough five-game run-in to come – after Chelsea, they go to Liverpool on Sunday and they must also play Manchester City at home. The club finished last season with 60 points.

“Absolutely yeah, absolutely,” Postecoglou said. “Clearly, clearly. As clear as you want it to be: 20-20. Definitely; 100%. What gives me my optimism? What I see. Playing our football, measuring ourselves against the best. The players have a real belief in what we’re doing. That’s all I need to see.”

Postecoglou has resolved defensive set-piece issues at his previous clubs, and most notably Celtic, and he is not remotely bothered about Spurs in this area, reacheding for a famous song lyric to reinforce his point.

“To quote Billy Joel: ‘You may be right, I may be crazy, but it’s maybe a lunatic you’re looking for,’” Postecoglou said. “Enough of you have done enough research on me to know this is not the first time I’ve been questioned about set pieces in my coaching career. Eventually I will create a team that has success and it won’t be because of working on set pieces.”