Pascal Lamy’s recent proposal to solve the Northern Ireland border problem in the context of Brexit is worth exploring further.

The former head of the World Trade Organization suggested that Northern Ireland be granted customs autonomy within the UK, then join the WTO in its own right.

As an autonomous customs region it could then elect to implement the current EU Customs Union rules.

This would avoid the need for any form of hard border on the Island of Ireland. It could go further and choose to mirror the EU single market rules.

Mr Lamy pointed out that membership of the WTO is not confined to sovereign states: any "autonomous customs territory" can become a member of the WTO.

Could the WTO help avoid a hard border after Brexit?

This is well known to the British government, as it negotiated the most famous example cited by Mr Lamy - Hong Kong and China.

Under the "one country – two systems" principle enshrined in the 1984 Sino-British Joint Declaration, Hong Kong was able to keep its membership of the WTO after the return of the island to Chinese sovereignty. China itself did not join the WTO until 2001.

Today China, Hong Kong, and the former Portuguese territory of Macau all have separate memberships of the WTO - even though they are all one country.

The legal key to separate Hong Kong membership of the WTO is the Basic Law of the Hong Kong Special Administrative Region (SAR), a Chinese law approved by the seventh National People’s Congress in 1990.

Article 151 states:

The Hong Kong Special Administrative Region may on its own, using the name "Hong Kong, China", maintain and develop relations and conclude and implement agreements with foreign states and regions and relevant international organisations in the appropriate fields, including the economic, trade, financial and monetary, shipping, communications, tourism, cultural and sports fields.

This enables Hong Kong, whilst a part of China, to operate a separate customs regime, and maintain a separate membership of the WTO (and other organisations such as APEC – the Asia Pacific Economic Co-operation organisation, which promotes free trade among members).

According to Pascal Lamy, something similar could be done for Northern Ireland that would facilitate the non-appearance of an economic border across the island of Ireland. It would require legislation from the UK parliament, and a functioning administration in Belfast.

Both would require the political will to do this. And that political will would also entail accepting different customs regimes - and the checks that come with them - between Northern Ireland and Britain.

This is politically very difficult, but may be the least politically and economically damaging way to a solution to the problems that have been so publicly brought home to the British in past week (but which have been in place from the very minute the last vote in the referendum was counted).

Economically it is a lot of trouble to go to for little return: North-south trade is small compared with the east-west trade carried out by both Northern Ireland and the Republic with Britain, especially England.

But both the EU and Brexit are political projects, and the decision to join or leave is taken primarily for political reasons, not trade and economic reasons.

This is why the Government has been so adamant that the solution to the Irish dimension of Brexit must be a top-down political solution, not a bottom up, complex assemblage of technical systems and trade arrangements that will yield their own political solution at the end of the process.

This is the leap in the dark that the Irish are not willing to take. Which is why the top level clarity of "one country - two systems" is of interest to the Irish.

The Hong Kong basic law, which flows from that top down concept, gives some other pointers to the kind of scope such an arrangement could have for dealing with the Northern Ireland border. For example, Article 152 says:

The Hong Kong Special Administrative Region may, using the name "Hong Kong, China", participate in international organisations and conferences not limited to states.... ...The Central People's Government shall, where necessary, facilitate the continued participation of the Hong Kong Special Administrative Region in an appropriate capacity in those international organisations in which Hong Kong is a participant in one capacity or another, but of which the People's Republic of China is not a member.

And in Article 153:

International agreements to which the People's Republic of China is not a party but which are implemented in Hong Kong may continue to be implemented in the Hong Kong Special Administrative Region. The Central People's Government shall, as necessary, authorise or assist the government of the Region to make appropriate arrangements for the application to the Region of other relevant international agreements.

In the context of migration policy, the Hong Kong basic law also has a pointer to potential solutions to Northern Ireland issues.

The basic law authorises Hong Kong to issue its own passports and ID cards. In Northern Ireland, the Good Friday Agreement grants the choice of Irish or UK citizenship to anyone born in Northern Ireland.

After Brexit, Northern Ireland will be the biggest concentration of people in a non-EU territory who are entitled to EU citizenship by birthright.

And in further precedent setting, the Basic Law states in article 155:

The Central People's Government shall assist or authorise the government of the Hong Kong Special Administrative Region to conclude visa abolition agreements with foreign states or regions.

It is also worth noting that the Sino-British Joint Declaration was registered as an international agreement at the United Nations - just like the Good Friday Agreement between the United Kingdom and Ireland.

The institutional memory of how to do this surely lives in Whitehall. The political expertise must surely reside in Chris Patten – the last governor of Hong Kong, a former EU Commissioner, a Tory cabinet minister, an expert on Northern Ireland, and a former chairman of the Conservative Party.

Sorry to stick this one on you, your Lordship.....