Harry the journeyman is ready to embark on his greatest adventure

After 27 years as a manager, Redknapp has reached the promised land of the Champions League – but a tax cloud hangs over him

As the Tottenham Hotspur bench spilled out onto the field on Wednesday night and ran towards the Spurs players and supporters in the far corner of the field, Harry Redknapp stood up, tugged his jacket into place and walked awkwardly over to Roberto Mancini for a handshake.

Redknapp does not do exuberant celebrations, not beyond the first few seconds of a Spurs goal that lifts him out of his seat – after that he reverts quickly to the state of anxious contemplation. The notion of the Spurs manager as a happy-go-lucky type who picks his team in a spare moment between leafing through the pages of the Racing Post is way off the mark – his success has been hard-won.

Securing Champions League football for Spurs this week has been the greatest triumph of Redknapp's career; greater even than the FA Cup at Portsmouth two years ago which subsequently was found to have cost the club so much. Portsmouth may have defeated Manchester United en route to the final but Tottenham have changed the very profile of English football, opening up the possibility that the "big four" cabal can be cracked.

It is the pinnacle of 27 years in management for Redknapp, a journey that famously began in 1983 with his Bournemouth team being beaten 9-0 by Lincoln City at Sincil Bank – a story that Redknapp recounted once again at the League Managers' Association dinner this season. He likes to joke that the sixth goal was offside and does not mind admitting that he wondered if he was cut out for the job.

He is a man who, those close to him say, is consumed by football. He often surprises his players by changing his line-up close to kick-off because it has occurred to him that tactically the team he has selected may be vulnerable. His knowledge of players in the lower divisions is comprehensive. He spends his spare time watching Tottenham's reserves. When it comes to the big games, like Wednesday nights, he is a gambler.

Against City, Redknapp once again demonstrated that he is a manager who is prepared to seize the moment. His team only needed to draw the game in order to close the deal for fourth place against Burnley on Sunday. Redknapp could have packed the midfield and tried to hold out, but he set up his usual 4-4-2 system to win the game.

This should be the happiest time of Redknapp's career. At 62, he is feted in his own profession as one of the greats, sharing a stage with Sir Alex Ferguson at LMA events; he finally has the big club he has always craved and a chairman in Daniel Levy who, although prudent to a fault, is prepared to back him in the transfer market. Redknapp is a grandfather and very close to his sons Mark and Jamie, the Sky Sports pundit.

But even as Tottenham take the plaudits for breaking up the old hierarchy of English football, Redknapp still lives under the cloud of a City of London police investigation that claims he failed to pay £40,000 in taxes on a payment to a Monaco bank account by Portsmouth chairman at the time Milan Mandaric. Redknapp was charged in January and the stress of the case is a constant accompaniment to his job.

It has taken a toll on Redknapp, who has been the subject of the investigation for 26 months and feels that his name has been smeared whatever the outcome. He denies all the allegations against him. But he is a man who has spent the last three decades of his career in the chaos of the football manager's job and he is a survivor in one of the most brutal professions of them all.

It will be interesting to see how Redknapp and Levy view the prospect of playing in Europe's elite competition and especially how it will affect the club's attitude to buying players. On the face of it, Spurs, in London, are an attractive prospect for foreign players and Redknapp will want to strengthen his squad, but Levy will be conscious of keeping the very tight ship he has run on course.

While Champions League revenue is one thing, the Spurs chairman also has to consider the possibility that his club will not qualify for the competition next season and he does not want to be left with a lot of expensive players on five-year deals. Not that Levy is ever likely to sanction the kind of six-figure-a-week wages that have become standard for the top earners at Chelsea, United and Arsenal.

It was obvious from the reaction of the Spurs team in victory that Redknapp has fostered a strong bond between his players. As for the barrel of ice water that was tipped over Redknapp live on the Sky Sports cameras, it was noticeable that – the excitable David Bentley aside – few of the senior players were involved. They know better than to test the patience of their manager.

Redknapp is a tough character, still capable of dominating the dressing room with his fearsome bollockings. But he is also a quiet man, never happier than when he is walking his dogs on the beach at Sandbanks with his wife Sandra. Last night, he was back at White Hart Lane with his son Jamie. The two Redknapps were managing opposing teams of fans in an event for charity.

Redknapp should be offered a new contract by Levy this summer: it is the very least he deserves for taking a team from bottom place in the league in October 2008 to the Champions League in less than two seasons. It feels like he has been around forever but in fact for Henry James Redknapp the journey is begun anew.

Who could spurs face?

Based on current league placings, Tottenham could be drawn against the following teams in the qualifying play-off in August:

Werder Bremen, Sampdoria, Seville, Auxerre.

Plus the winners of the five ties between the following 10 teams:

Zenit St Petersburg, Ajax, Dynamo Kiev, Celtic, Braga, Basel, Burzaspor, Brugge, Unirea Urziceni and the Greek play-off winners.