The first early warning of it came three weeks ago at Wembley, when Tottenham tore into Chelsea and ripped them into little pieces. Beating Southampton and Leicester City last week was impressive too, but the real emphatic proof came on Tuesday night when Spurs went to Barcelona, with their European season on the line, gave away an early goal but fought back to have the better of a famous 1-1 draw. It was one of the best and most important results of the Mauricio Pochettino era.

It is now a familiar sound in mid-December, the sound of Tottenham Hotspur whirring up through the gears. Just when other teams start to flag, Spurs find that they can press harder, pass sharper, and start to drive the opposition off the pitch. And the implication of the last few weeks, and especially Tuesday at the Nou Camp, is that we are heading in Spurs season once again.

At their best Spurs play an athletic, expansive game, defending high, pressing high, using every last inch of the pitch. More than anything else it requires the coordination of years of coaching from Mauricio Pochettino and Jesus Perez, and the perfect physical conditioning of the players, to ready them to run and run and run where Pochettino commands.

The whole Pochettino coaching regime is done to enable this. Those long exhausting pre-seasons, the Gacon tests, (running for 45 seconds, resting for 15, getting faster and harder as it goes), all the sports science, the meticulous measuring of every player’s performances and output, it all works to get the squad in peak physical condition for the most important phases of the season.

And the worrying news for Burnley, Everton, Bournemouth, Wolves and Cardiff, their next five Premier League opponents, (they also have a League Cup quarter-final at Arsenal), is that the history books show that this is when Spurs play some of their best football. A quick look back over the four Pochettino seasons so far shows that they play some of their best football in this Christmas spell - between their final European group game in early December, and their FA Cup third round game in early January.

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All four seasons, in this Christmas spell, Spurs have averaged more points per game and more goals per game than they averaged over the rest of that season, showing that they do in fact play to a higher level at this time of the year.

All the way back in 2014/15, Pochettino’s first season, Spurs had a strong Christmas spell, winning four of their five Premier Leagues and picking up 13 points, at an average of 2.6 points per game that was higher than their season average of 1.68 points per game. They scored 11 goals, at 2.2 per game, much better than their season average of 1.53 goals per game. The centrepiece was a 5-3 thumping of Jose Mourinho’s Chelsea at White Hart Lane on New Year’s Day, a result that took the league by surprise.

But the next season the rest of the Premier League had been warned and Spurs still stepped it up over Christmas. From their five league games in 2015/16 Spurs won three, picking up 10 points, at a better rate (2 per game) than their season average (1.84).

Even in Spurs’ best season of the modern era, 2016/17, they managed to go up a gear over Christmas. After losing 1-0 at Old Trafford on 11 December, they then won seven straight, making for a 15-point, 15-goal haul from their six games within our ‘Christmas period’. It was title-winning form: 2.5 points per game equates to 95 points over a 38-game league season.

Tottenham find a way to kick on when other teams begin to lag (Getty)

That was arguably the best football Spurs have ever played under Pochettino, with Danny Rose and Kyle Walker bombing forward from wing-back in a 3-4-2-1 system, as they won 4-1 at Southampton and at Watford. Best of all came when Antonio Conte’s Chelsea came to White Hart Lane, on a then-record winning streak of 13 straight games, only for Spurs to beat them 2-0. It was not enough to beat Conte’s Chelsea to the title, but it was one of the last great nights at the old ground.

And then last season, with Spurs playing on the road, they still did better than ever. Squeezing in seven league games in this spell, they picked up five wins, and those 16 points (2.29 points per game) was better than their season average of 1.95 points per game. As with the previous year, they went on a festive goalscoring binge too: they put five past Stoke, five past Southampton, getting 19 in total. Average that out over a whole season and you get 103 goals.

Central to all of this is Harry Kane, who scored eight of those 19 goals, including consecutive hat-tricks against Burnley and Saints. He explained last week why he finds this period so fruitful.

“It’s these sort of periods in my career where I’m at my best”, Kane reflected. “It might be down to fitness as well. When teams are tired I exploit the space a bit more. In December, January I hit top form.”

Harry Kane knows that both he and Spurs hit their stride over Christmas (Reuters)