The Commons today became a dignified part of the constitution. David Cameron led the tributes to the Queen on the day she becomes our longest-serving monarch. Harriet Harman followed him in quoting the memorable phrase, “my whole life whether it be long or short”, used by the Queen in the broadcast dedicated herself to our service which she made while still a princess from South Africa on her 21st birthday.

Those words were drafted for her by Dermot Morrah, a distinguished member of the Times’s editorial staff. It is remarkable that 68 years later they still apply. The tributes to her were entirely fitting.

At the start of PMQs, Cameron added a short tribute of his own to Harman. This too was fitting: Labour’s interim leader has many admirable qualities, and might have been a better bet than whoever is unveiled on Saturday as the next Labour leader.

But one does not want too much of that sort of thing. Ours is an adversarial system, in which the two sides compete to make each other look undignified and incompetent. The duty of the Opposition is to oppose, but Harman in a measured tone asked some worthy questions about refugees.

High-minded people would like the Leader of the Opposition to strike that note every week. If he or she did, PMQs would command a much smaller audience.

Two Labour MPs made gallant attempts to raise the volume, or lower the tone. Debbie Abrahams (Oldham East and Saddleworth) accused Iain Duncan Smith of “breaking the ministerial code” and also of making “offensive remarks” about disabled people. Jo Cox (Batley and Spen) asked whether the Prime Minister has “led public opinion on the refugee crisis or followed it”.

Cameron was able to reply to the latter point that the Government has led public opinion on the 0.7 per cent international aid commitment. As he staked his claim to the moral high ground, the Prime Minister displayed a positively Blairite self-assurance.

How fascinating it will next week be to watch Jeremy Corbyn – provided he does indeed become Leader of the Opposition – try to shake Cameron by showing some Bennite self-assurance.