As Labour MPs limped back to work after making their contributions to Tuesday’s bruising welfare debate, a sharp-suited and silver-tongued party heavyweight loitered at the top of the Portcullis House escalators, glad-handing each and every colleague that passed him by. 

One parliamentary bag-carrier tells me he was “wreathed in smiles”. If only David Miliband had shaken a few more hands in the autumn of 2010 perhaps it would now be him at the despatch box each Wednesday lunchtime. 

Nearly two and a half years on, he is once more a man on a mission. 

He might not have much time to attend the mother of parliaments these days, but Ed’s big brother is still box office. Like his party leader, David is at heart a politico, a geek, and an Oxford-educated son of a Marxist academic, but he still has that certain something Ed lacks. 

There had been murmurs of a comeback for days, and it was tangible how, as Miliband elder’s speech progressed, tittering turned to subversive chatter. A few rows below, Ed Balls refused to turn his neck. David’s admission that “I did not get good marks in maths” will have done little to placate him.

But could the former Foreign Secretary really knife the Shadow Chancellor? It would take Machiavellian scheming of the kind Team Balls would be proud of. Indeed it was no coincidence that they hit back with full force yesterday. 

“Allies of the Shadow Chancellor”, which Westminster village types know almost certainly means the poisonous spin-merchant and Balls confidant Alex Belardinelli, briefed Kevin Maguire that: “he’d take his bat and balls away and retire to the back benches rather than swallow demotion to another portfolio”. Ed Miliband had his warning: mess with Balls and he would live to regret it.

The Shadow Chancellor’s stuttering performance in his response to the Autumn Statement in early December is not reason enough to fire him, even if he deserved it for his laughable attempt at smearing his critics as bullies. Much more serious are Balls’s deeply damaging poll ratings, which still fail to take advantage of George Osborne’s, shall we say, not exactly Olympic popularity. 

Balls is forever tainted by the curse of Gordon Brown. His economic crimes in the heady days of 2008 will never be forgotten, a key sticking point for Labour in 2015.

In spite of his weaknesses, Balls still commands respect, hatred, and most importantly fear. The Prime Minister’s utter contempt for the Shadow Chancellor, betrayed each time he loses his cool with the man muttering from a sedentary position, cannot be underestimated as a reason to keep him. Political parties need people like Ed Balls: bruisers who can do battle.

Most of all it would take a brave man to declare war on Labour’s fiercest personality. When he is fed up with making his millions in the private sector, David Miliband will almost certainly return to frontline politics one day. 

If he has the Shadow Chancellor in his sights then he better beware. As many an axed Labour frontbencher can testify, Ed Balls has committed political murder time and time again throughout his career. He would not hesitate to do it again.

Alex Wickham is The Commentator's UK Political Editor and a reporter at the Guido Fawkes website. He tweets at @WikiGuido