James Lawton: England's greatest threat is their own complacency. This series is not won yet

The sweet arrogance of youth may be wonderful but there has never been a dose of it not helpfully diluted by a little experience of grown-up life. If this is indeed true, let us hope Steve Finn, aged 21, acquires in a hurry the required amount.

It might just help him avoid being smeared from one end of Australia to another when the battle for the Ashes starts in November.

Finn, let's be fair, is a promising prospect. At 6ft 8in, he went at the overwhelmed Bangladeshi batsmen like a force of nature earlier in the year and he's had his moments, though sharply less frequent, against a Pakistani team which for two Tests appeared to be learning to bat by numbers.

Yet if he suggests he has much of the right ability to make a sustained impact at the highest level of the game, does he have the right attitude?

This week's evidence is not encouraging. His remark that Pakistan, who so brilliantly turned back the tide at The Oval, are a "collapse just waiting to happen" at Lord's over the next few days would have been graceless on the lips of some old pro sledging a cowering young opponent.

Matt Prior did plenty of that at The Oval, along with the close-fielding cordon, and it was fair enough. But when Azhar Ali and Mohammad Aamer, aged 18, held their nerve they were entitled to a degree of respect. They had achieved a rite of passage.

Certainly, it was something that might have been ceded to them, at least until the battle recommenced, by opponents experienced enough to know quite what it is like fighting to establish yourselves in the Test game against formidable odds. It didn't come from Finn, however, which is worrying in that few Test neophytes can ever had an easier ride into the big time than the big man of Middlesex.

Until the arrival of the glacial calm, and clear influence, of Mohammad Yousuf at The Oval, Finn had won his headlines while breaking the eggshell batting of Bangladesh and then supplied respectable support work breaking down resistance equally negligible from Pakistan. It was a different picture with Yousuf around, of course. Pakistan's blood began to pulse more evenly – and Finn, the shock trooper, finished up with match figures of 1 for 92.

It was a signal for Australian opener Shane Watson to single out Finn for his inexperience and suggest that he will be targeted with some precision come the opening of hostilities in Brisbane. Routine propaganda, of course – and no doubt it is a category in which Finn's dismissal of the Pakistanis might be placed.

However, Watson does have a little sweat and sun on his brow, and you could say that he was speaking of something he knew. Finn's assumption that he could so brusquely trash a team that had just beaten his own in a memorable Test match, and from a position of such slender, and favourable experience, rather more than hints at the old English disease: a self-belief that is maybe too quickly acquired, and too easily shed.

As it may happen, Finn could well be proved right at Lord's. If Pakistan bravely regained their pride, initially through the brilliant bowling of Aamer and Saaed Ajmal, their batting did waver again at the climactic phase, and maybe it is asking a lot to assume that all of their demons will disappear into the leafy streets of St John's Wood today. More significant, though, to England's prospects in this Test – and in Australia – is their own ability to purge some alarming weaknesses.

The main one has been highlighted, however unconsciously, by one of their least experienced players. Grudging in his acknowledgement of the Pakistanis' comeback, dismissive of the character that was displayed in one of the darker passages of their nation's history, Finn hits a familiar note: one that plays to the habit of premature celebration of victories that still have to be gained, on this occasion against sharply improved opponents.

Such a leaning has already been mourned by England captain Andrew Strauss, who has accepted for some time that his great enemy, apart from the loss of his own form at a critical point, is his team's history of complacency. His predecessor Michael Vaughan railed against such danger after the Ashes of 2005, swearing that his great challenge was to keep his team honest, aware that one triumph means nothing unless it is a spur to greater achievement.

The injured Vaughan was forced to witness the results of English negligence, the grim ritual of an Ashes whitewash.

Such a fate may not necessarily beckon now but the reality is that England, seven months after surrendering to South Africa in a series that appeared to be won, are again faced with the possibility of a crushing anticlimax. We can sure of one thing. Mohammad Yousuf's eyes will surely have narrowed at the first callow talk of another batting collapse.