There are many contenders for the title of ‘Nadir of the 2017-19 Parliament’, but a strong one must surely be the events leading up to the eventual passage of the ‘Benn Act’ – the legislation that saw the House of Commons take improper control of the Government’s agenda.

Making the case for it, Oliver Letwin said that the legislature would effectively become the Cabinet. I pointed out the many, many problems with this idea at the time.

Whilst nothing so noxious is likely to reoccur any time soon, not least because Sir Lindsay Hoyle now sits the Speaker’s chair, it was the culmination of a longer-running trend towards the Commons starting to exercise powers traditionally reserved to the Government.

On one level, this does increase accountability. But it does this at the cost of making government less effective.

This is most obvious in the case of deploying the Armed Forces. Tony Blair’s innovation of seeking Commons approval for military action, alas not yet completely shaken off, rendered the United Kingdom a less reliable partner to our allies. David Cameron lacked the authority his predecessors had to commit British forces – and Ed Miliband had an opportunity to pull the rug out from beneath the Government for short-term political gain.

All this provides some important context to demands, reported in yesterday’s Financial Times, for MPs to be given a greater say over the negotiation of trade deals.

At present, the Commons may vote down deals negotiated by the Government. But apparently there needs to be more scope for ‘holding the Government to account’. This presumably means finding some role for the Commons whilst deals are being negotiated (although surely not, deo volente, in their negotiation).

More accountability always sounds attractive. But the trade-offs are real. There is a risk to freighting the conduct of government with too many ‘checks and balances’. The duties and mandates of individual MPs are not, after all, the same as those of the Government. Their ultimate obligations are to their constituencies, and not the nation as a whole. Few but the most diligent will likely be across the full sweep of a detailed treaty negotiation.

As was pointed out during the row over the Benn Act, the proper means for Parliament to oversee executive functions is to delegate them to a body it has chosen – the Cabinet – and then hold it to account for how it wields them. Accountability does not require the legislature to start more directly involving itself in executive functions, especially not on a piecemeal basis.

Blair farmed out responsibility for committing troops in order to share the blame around and make it harder for MPs, who had to vote without access to all the information, to subsequently hold him to account. Ministers should be very wary of building on that legacy.