Parliament’s current impasse is the culmination of a domestic political failure to solve an trilemma which has, in various forms, been left unresolved since the UK’s first attempt to join the then European Economic Community (EEC) in 1961.
The PM and the Brexit negotiations process have determined that parliament must choose between a maximum two of three options: 1) customs and regulatory alignment with Europe; 2) no hard border with Ireland, and; 3) an all-UK solution.
These same red lines arose 60 years ago.
The move towards Europe began in 1959 when both Britain and Ireland both decided to establish diplomatic relations with the EEC. However, there were fears in Dublin that the EEC might approve the UK application but reject Ireland’s owing to its as yet under-developed economy.
Irish Taoiseach, Seán Lemass, warned that a UK-only entry would alter the customs and regulatory arrangements at the UK-Irish border in a way that would be very damaging for the island of Ireland, both for the all-island economy and for peace.
Around the same time the IRA had begun its Border Campaign. Attacks on customs posts and administrative infrastructure in Northern Ireland led the British Government to request Dublin to implement checks of goods and travellers crossing the border.
Dublin refused for much the same reasons as they insist on no hard border today. Westminster instead began to explore alternative arrangements for Northern Ireland.
However, the Stormont Prime Minister Lord Brookeborough refused to sanction any arrangements which did not apply to the United Kingdom as a whole, characterising the Irish Government’s insistence on no checks at the border as "the first step in moving the border to the Irish Sea"
This, Brookeborough feared, would weaken Northern Ireland’s constitutional position within the UK. In familiar terms to today’s, he and other unionist leaders talked of a supposed hidden plot by Dublin.
Many MPs in Westminster were reported to be exasperated with the Unionist’s attitude to all-island economic co-operation to solve the border problem, believing Unionists had sacrificed Northern Ireland’s economic interests for their political ideals.
Sir Horace Algernon Fraser Rumbold, Deputy Under Secretary of the Commonwealth Relations Office, was quoted describing Unionist attitudes as "dog in the manger" stuff.
When British Prime Minister Harold Macmillan tried to lead a divided Commons and Country to join the EEC in August 1961 his options were thus constrained by the wider geopolitical setting in which the UK still operates: our interdependence with our neighbours and trade partners.
Despite vociferous opposition from his own back benches, Macmillan made clear that that “we shall not take the final step unless our Commonwealth and other obligations can be reconciled”.
The Cabinet was divided and there were calls for a new leader. A hard right Tory back-bench group, the Monday Club, began coordinating with Ulster Unionist MPs to attack and undermine the PM. The Tory party was even rumoured to be on the verge of splitting over its EEC divisions.
In an attempt to convince his doubters, the PM began repeating select political slogans ad nauseam every time he was interviewed, for which he was widely ridiculed in the press.
He also made appeals to the opposition for support, but without success. The Labour Party wanted a general election.
In the end, European (especially French) leaders’ distrust that Britain would stick to its commitments meant the UK was not permitted to join the EEC until both the UK and Ireland did so together in 1973.
Instead the UK opted to join the European Free Trade Association (EFTA), established as an alternative trade bloc for those states that were unable or unwilling to join the then EEC.
The main difference between the EEC and the EFTA was that the EFTA did not operate common external customs tariffs. Each EFTA member was free to set its customs duties and negotiate its own free trade agreements with countries around the world.
This compromise assuaged those opposed to the UK being a member of the European Project while still allowing the UK some of the benefits of access to the European market.
Fast forward to 2019. On Tuesday, Parliament will again attempt to reach a decision on this trilemma it has been unable to resolve for 60-odd years. While a half-way-house EFTA/EEA is again possible, the key difference this time is that ending up with no deal is not an option.