John Bercow needs to be careful. His tendency to jump from placid calm to apoplectic rage may be endangering his political, as well as his physical, health.
Even catching the deflected anger of Bercow's rage is alarming. I have only just recovered after viewing his monstrous attack on Conservative MP Graham Stuart, seen from perhaps ten feet above Bercow's throbbing forehead veins, during Gordon Brown's speech to the Commons earlier this week.
It was difficult to concentrate on the ex-prime minister, droning away somewhere on the left of Bercow's enormous Speaker's chair. Not because the contents of his speech were not weighty and significant, but because of the determined attempts by Tory backbenchers to disrupt his flow.
"Will the right hon gentleman give way?" Graham Stuart asked. Brown replied: "I want to set out the facts for the House and will be happy take any interventions after."
This was unusual behaviour from the Rt Hon member for Kirkcaldy and Cowdenbeath, even if he is a former prime minister. Stuart wasn't having any of it. It was after he had repeated the question twice more that, apropos of nothing, Bercow exploded.
Hansard records the Speaker's remarks thus: "I am going to say it to you once and once only: you are far too excitable. Be quiet and calm down—[ Interruption. ] Order. If you cannot—do not shake your head at me—then leave the Chamber."
As usual, the official record presents a soberer version than the reality. While the above was being said Labour backbenchers were shouting away, roaring "sit down!" at Stuart. At one point an opposition MP went further, venturing: "Sit down, stupid!" Hansard did not record these remarks. Nor did it convey the full extent of Bercow's bile. I would propose they amend their version with this: "DON'T SHAKE YOUR HEAD AT ME!"
Stuart gaped, shrugging with his left hand sprawled along the back of the wooden bench. He waited just a few seconds, his eyes never leaving Bercow's - before shaking his head defiantly once more.
It was clear that the Tory benches felt strongly that an injustice had been committed. It was the sudden violence of Bercow's attack which was so alarming. Ben Gummer, sitting directly behind, openly congratulated Stuart.
All of this would have been a 'by the way' if it was not for the fact it took place just a few hours after prime minister's questions, when the Speaker came closer than he ever has before to completely losing control of the House.
The rabidly enthusiastic Tory cheers at the end of David Cameron's final reply to Ed Miliband continued, chillingly, over the following refrain: "Order! ORDER! ORDER! ORDER! ORDER! (pause, helpless smile) Order! Order!"
Several hundred MPs were defying Bercow. They continued for 17 seconds - quite a long time to defy the Speaker, when you think about it - but when the din finally died down Bercow picked out children's minister Tim Loughton for special treatment.
"It is not funny," a by now very hoarse Bercow croaked. "Only in your mind, Mr Loughton, is it funny. It is not funny at all; it is disgraceful."
"Me thinks Speaker Bercow needs to calm down dear. 3rd time with same childish put down and I wasn't actually saying anything."
Bercow's reforms have helped turn parliament around since the expenses scandal of 2009. When you compare his loyalty to the interests of backbenchers with the more relaxed high-handedness of his predecessors, there's no comparison. The problem is that as he clamps down on the Tories - and it is invariably the Tories he picks upon - he engenders a sense of injustice which lingers longer every time.
Perceptions shape reality. The suspicion that Bercow has a natural predisposition towards Labour, whose support secured him the election against Tory favourite Sir George Young, deepens with every incident.
The Speaker must be careful when parliament returns this autumn. If he's not, another wave of Tory backbench manoeuvring against him will become not a risk, but a reality.