It's maddening isn't it? When he's in the zone, he plays as if he has no peers, bullying his opponents into submission with a technique so effortless that it seems nothing should ever go wrong. But then everything does go wrong - his balance shifts ever so slightly off-centre, and like the stacks of pennies that fine-tune the pendulums of Big Ben, one miniscule misplacement throws the entire mechanism out of kilter.
To whom am I referring? Steve Harmison? ... or Marcus Trescothick? In fact, the description could apply to both. Today, we saw an angry riposte from the one man, and another depressing failure from the other, and yet it could so easily have been the other way around. That's the deal with these two performers. They are England's all-or-nothing men - 11 wickets here, a brace of single-figures there. As such they are probably the most inscrutable characters in the England dressing-room.
Harmison was as enigmatic as the Mona Lisa as he fronted up to the media this evening. The morning papers had been merciless in their criticism - "It's Stephen Harmlesson" mocked the Daily Express after his first 15 (wicketless) overs had been clattered for 78. Today's analysis read like a two-fingered salute - 15.4-4-47-4 - as his comments afterwards amply confirmed.
"I didn't feel right yesterday," he muttered through an uncharacteristically stony-faced expression. "I don't know [what happened], I just didn't feel right. I can't put my finger on it, but it doesn't frustrate me one bit. I went on the field yesterday the same way I did today. Everyone has an off day. The whole team has had an off Test match."
The debate about Harmison's form and fitness (physical and/or mental) is gathering steam as surely as the Ashes bandwagon is rolling into town (96 days and counting, in case you escaped last week's cake-cutting hype). Reports of a back problem have been doing the rounds of late, although Harmison's own take on the situation implied it might be more of a soft-tissue issue further up his spine. "There's something in my side/back area that's causing concern," he eventually volunteered. "It's something new, but I'm not going to use that as an excuse because I didn't bowl very well yesterday."
Either it is a problem, in which case he needs a break from the grind and a chance to freshen up before the winter, or it isn't. But all this verbiage is about as substantial as the froth on a Starbucks cappuccino. Unless both he and Trescothick get run over by a baggage handler as they arrive at Brisbane Airport in November, there is absolutely no chance of England beginning their defence of the Ashes without them. For all the PC noises about avoiding dead-rubber syndrome, Harmison and Trescothick epitomise the singular lack of urgency about England's performance in this game.
Harmison didn't even try to hide his sense of "job done", as he flipped off his indifferent start to the game in a statement that dripped with complacency. "I've taken 20 wickets in four Test matches. Is that a worry? I don't think so. It will be a worry if somebody stops picking me, but I'm not worried that that will happen. I feel as though i contribute to the team, I feel as though I do a good enough job. Every time I pull that jumper on I feel as though I'm giving it everything. If 20 wickets isn't enough I'll have to work harder."
In actual fact, if England's stated aim is to get 20 wickets per Test every Test (as it should be), then Harmison's haul - as part of a four-man attack in a four-Test series - equates to precisely his share, no more, no less. It's all very egalitarian, but those are not exactly the sentiments that should be pouring forth from England's leading strike bowler. He's become the undroppable enigma, and he knows it.
Talking of undroppable, let's come back to Trescothick - a man who, famously, has been an automatic pick ever since he debuted against West Indies in 2000. "Marcus Trescothick has got five-and-a-half thousand runs in 75 Test matches for England," said Harmison, demonstrating an impressive head for figures (in fact it's now 5825 in 76). "He's a world-class performer, and that's the thing the whole country's got to realise. He's scored runs for fun [in the past] and he'll come back. If it had been a young lad, there might have been cause for concern. With Marcus, there are no concerns. If he goes through a bad trot, his good trot might be in Australia, which would be great for England."
The ridiculous thing is that it is probably true. Trescothick has managed as many runs in the series - 135 - as Kevin Pietersen produced in his single century at Headingley, leaving him with an average of 19.28, which is scarcely six runs healthier than the much-mocked Monty Panesar (his four not-outs in five innings notwithstanding). The only comparable period was his tour of woe in the Caribbean in 2003-04, when he strung together six single-figure scores in a row. England kept faith, however, Trescothick responded with 130 and 82 in the subsequent one-day series, and come the summer he was back on cruise control.
You see, it's all froth. Nine hundred and eighty-three words of it on this occasion, and apologies for that. England fly to Brisbane with a clutch of class performers whose form is currently temporary. They'll either be alright on the night or they won't be, and in the meantime we'll work ourselves into a lather trying to get into their heads. Welcome to the countdown to Ashes mania, 2006-07. It's going to be a fascinating and maddening few months.