Mr Balfour’s poodle still has a few teeth left to leave its mark on Brexit

While the House of Lords has an important role to play, these are uncharted constitutional waters

With perfect timing, English National Opera is staging a new version of Gilbert and Sullivan’s political satire, Iolanthe. Today, the curtain goes up on the committee stages of the EU Withdrawal Bill in the House of Lords, the principal target of the comic opera’s finest barbs. “When Wellington thrashed Bonaparte / As every child can tell / The House of Peers throughout the war / Did nothing in particular / And did it very well.”

So, what are their lordships proposing to do about Brexit – nothing in particular, or some serious damage? The conventional wisdom is that they will huff and puff but will not bring the house down. The Commons has already passed the Bill and it is the job of peers to improve it, not wreck it – especially when the matter with which they are grappling is the consequence of a nationwide referendum: how can an unelected chamber gainsay the “will of the people”?

Would that not be unconstitutional? Yet there is little written down in statute or rooted in convention to cover the current imbroglio.

The Upper House today is a very different place to the chamber lampooned by G&S, no longer stuffed full of the hereditary aristocrats who were mostly removed by the Labour government. Indeed, even though as the Prime Minister observed yesterday the Lords is far too big and needs to be cut back, there are actually fewer peers than there were before 1999. The difficulty now is that most turn up for business and cram on to the red benches whereas, back in the day, Iolanthe’s Earls of Tolloller and Mountararat would have left their ancestral piles once in a blue moon.

In the 140 years since the operetta was written, the House of Lords has had its wings clipped on many occasions, eventually losing the fight for supremacy to the Commons in 1911. The Parliament Act of 1949 circumscribed its power yet further. It has no authority, for instance, to thwart financial measures, though that did not stop peers voting down tax credit changes proposed in the 2015 Budget and three times upheld by MPS. This was possible because, owing to the removal of the hereditaries, the Opposition has a majority in the Upper House, with 296 Lib Dems and Labour peers to 248 Tories, with the balance held by crossbenchers. This makes the Government vulnerable to ambush; and it would be surprising if it got through the next few weeks unscathed.

Ten days have been allocated for the committee stage, ending on March 26, and amendments have already been piling up – 83 pages of them as of last Friday. They include demands for a second referendum; the removal of the so-called Henry VIII powers giving ministers the ability to change law by diktat; and a requirement that the UK remains inside the EU single market and the customs union.

One of the biggest fights could come over the powers of the devolved governments and assemblies. The Government envisages that, after Brexit, the devolved administrations will have direct powers over 111 areas of policy-making currently in EU hands, including fishing, agriculture, food labelling and environmental standards. Ministers hope such a transfer will lay to rest the accusation that they are using the UK’S departure to reassert Westminster’s control.

But at talks this week Scottish ministers are set to reject the proposal, because the UK government will retain a veto over the use of some of these powers until “common frameworks” are agreed to avoid disrupting the internal British market. This matter was not resolved during the Bill’s Commons stages and could become a rallying point for antibrexiteers in the Lords, though the Government can presumably forestall a defeat by removing the veto threat. Nonetheless, it would be hard to accuse the Lords of overstepping their powers because these are uncharted waters for Parliament.

There is another devolution hurdle to negotiate. Can the Bill become law without the consent of the devolved legislatures? The law requires that they approve measures that affect them but does this mean they have a veto? The Government says not; but does anyone really know? This might have to be settled in the courts. The Scottish government has even drawn up a Continuity Bill to protect its laws from the impact of Brexit in the event of consent being withheld by the Holyrood parliament.

So, while everyone is preoccupied with Thursday’s Ministerial showdown at Chequers to discuss trade, customs agreements and the Irish border, a stand-off with Scotland is threatening to tighten the Gordian knot of Brexit still further.

In the coming weeks, peers will also vote on whether there should be a second referendum to approve the final agreement. Would it be unconstitutional to agree such an amendment when the Commons has rejected the idea? The Lords are entitled to ask MPS to consider this matter again; they would overstep the mark only if they insisted upon getting their way, forcing the Government to use the Parliament Act to override their objections. For good or ill, we have a bicameral system of governance and need to live with it; and that means recognising the proper role played by the Lords.

Early in the last century, when a Conservative backbencher called the Upper House “the watchdog of the constitution”, Lloyd George replied that it was “Mr Balfour’s poodle” (Balfour being the Tory leader). But even though it has had most of its teeth removed, it retains an important function defending the integrity of our political structures. Otherwise the Commons really would be the untrammelled “elective dictatorship” identified by Lord Hailsham.

Our constitutional settlement relies on all the component parts working as harmoniously as possible, including the Lords. It may well be what Viscount Ridley called “a gilded, crimson echo-chamber for Remain” but it knows where it stands in the great scheme of things.

Over the next year or so before we leave the EU, the wiser heads on both sides of the Brexit divide need to ensure that the House of Peers does nothing in particular, but does it very well.