The announcement Lynton Crosby has been recruited to the Tories 2015 campaign team spells trouble for the Labour Party. Big trouble.

Crosby is what’s euphemistically called a “divisive figure”. And it’s true, he does divide opinion. Those whose opinions and judgment are sound, rate him. Those whose opnions aren't, don’t.

When he was first appointed to work for Michael Howard, Conservative Central Office (CCO) officials were unsure what to make of him. Then one day they started receiving a series of irate calls from John Redwood, who felt he was being sidelined from the Tory Party election effort. Finally Crosby said, “Let me talk to him”, and picked up the phone. “Sorry John,” he told the startled shadow minister, “ but the voters don’t like you so we’re keeping you in the background. Anyway, I’ve got to go now. Speak soon”. From that moment on, every time Crosby would come out with one of his famously blunt statements Tory officials would shrug and explain it away with two words: “He’s Australian”.

That robust style has led to accusations Crosby deals from the bottom of the deck, especially on issues like immigration. And it’s true that he pushed some tough messages when working for both John and Michael Howard. But his critics conveniently ignore the fact he also crafted the messaging for Boris Johnson, the man who is more liberal on immigration then any other senior Tory politician, as well as a fair few Labour ones.

Labour’s official line is Crosby is a big fish who has spent the last 8 years swimming in a relatively small mayoral pond. A couple of days ago Alastair Campbell blogged: "The only time I saw his work close up, in the 2005 general election when he was Michael Howard’s strategist, if it was really his campaign, it was hard to be impressed”. Other Labour insiders, though, are more circumspect.

In September Tim Montgomerie penned an article for the Times that sent a shiver through the shadow cabinet. It spelt out how the Tories were finally preparing to take the fight to Ed Miliband, and detailed what Tory strategists believed were Labour’s weak spots. They dovetailed precisely with what those within the party had themselves identified as the vulnerable areas of their operation. And they worry Crosby is the man to target them.

Crosby’s image is very much that of a classical spinner, in the mould of a Campbell or a Wheelan. But in reality his engagement with the media is limited, and his real strengths lie in the areas of strategy and organisation.

“When Lynton first came in he spent the first week just reading and watching”, said one veteran of the 2008 London mayoral campaign. “Then we got a call from the BBC telling us the date of the first debate, which was on transport. Lynton looked up and said “We’re not doing it”. People did a double take - it was the main BBC debate. He said “No transport, no health, no housing They’re Labour issues. Tell them we’ll do it on the economy, crime or investment, or we’re not coming”. The BBC agreed.

On organisational issues he was equally focused. Crosby created the now-famous “Donut Strategy”, in which the Tories focused their resources on the outer London boroughs, effectively ceding Livingstone’s inner London heartlands. But he also took an almost obsessive interest in the micro-detail of what at the time was a creaking turnout operation. “When he arrived, he asked who we had managing the key boroughs and wards,” said one insider. “CCO told him, 'Don’t worry, we’ve got good people in there'. Lynton said 'OK, I want their names.' Of course it turned out there were big gaps. But Lynton filled them."

Labour insiders worry that Crosby’s appointment has exposed gaps in their own operation. One pointed me to an article by Rowenna Davis in last week’s Guardian, which highlighted the work of Ed Miliband’s organisational expert, US community activist Arnie Graf. "The party that just says 'vote for me' isn't worth very much”, Graf is quoted as saying. "The idea of becoming a relational party is starting to come together… there is a huge appetite for what we are doing”.

The contrast with Crosby couldn’t be more stark. “Basically it’s the Guru against the Hit Man”, said one Labour source. “You’re putting nice community politics up against a rapier-sharp campaign operation”.

This echoes a concern a number of Labour officials have had for some time. Whilst Ed Miliband is credited with bring some discipline to his day to day media operation, there are still big strategic gaps. “Who’s his Mandelson?” said one shadow cabinet insider.

Within Tory ranks there is excitement - and a little trepidation - that “The Australian is back”. But on the Labour side there is alarm. The big fish has found big waters to circle in.