Heard the one about the entire population of Hong Kong being moved to a new city specially built for them in Northern Ireland?

It may sound like the start of a bad joke, but when the idea reached the ears of Whitehall mandarins they gave it some serious thought… about how to bat it away, at least.

The bizarre plan was the brainchild of Christy Davies, a lecturer at Reading University who warned that when Britain handed back Hong Kong to China in 1997 there would be no future for its 5.5million inhabitants, newly-released files at the National Archives at Kew show.

Future plans: A lecturer at Reading University had warned that when Britain handed back Hong Kong (pictured) to China in 1997 there would be no future for its 5.5million inhabitants

Resettling them in a new ‘city state’ to be established between Coleraine and Londonderry could revitalise the stagnant Northern Ireland economy, he added.

The province only had a population of 1.8million at the 2011 census.

When details of his scheme appeared in the Belfast News Letter in October 1983, they caught the eye of George Fergusson, an official in the Northern Ireland Office.

He fired off a memorandum to a colleague in the Republic of Ireland Department of the Foreign Office, declaring: ‘At this stage we see real advantages in taking the proposal seriously.’

In the countryside: Resettling the inhabitants of Hong Kong in a new ‘city state’ between Coleraine and Londonderry (above, file image) could revitalise the stagnant Northern Ireland economy, the lecturer said

Among the benefits, he suggested, was that it would help convince the Unionist population that the government in Westminster was truly committed to retaining Northern Ireland in the UK.

The arrival of 5.5million Chinese in Northern Ireland may induce the indigenous peoples to forsake their homeland for a future elsewhere David Snoxell, Foreign Office

It is not clear whether his tongue was in his cheek when he wrote, but by the time the reply came back two weeks later from the David Snoxell at the Foreign Office, somebody had twigged that the idea was perhaps not entirely serious.

Mr Snoxell drily replied: ‘My initial reaction, however, is that the proposal could be useful to the extent that the arrival of 5.5million Chinese in Northern Ireland may induce the indigenous peoples to forsake their homeland for a future elsewhere.

‘We should not underestimate the danger of this taking the form of a mass exodus of boat refugees in the direction of South East Asia.

Location: Among the benefits, it was suggested, was that it would help convince the Unionist population that the government in Westminster was truly committed to retaining Northern Ireland in the UK

‘On the other hand, the countries of that region may view with equanimity the prospect of receiving a God-fearing, law-abiding people with an ingrained work ethic, to replace those that have left.’

My mind will be boggling for the rest of the day Foreign Office employee

Worse, he added, the plan could have serious implications for the UK’s dispute with Dublin over the sovereignty of Lough Foyle.

He wrote: ‘The Chinese people of Hong Kong are essentially a fishing and maritime people.

‘I am sure you would share our view that it would be unwise to settle the people of Hong Kong in the vicinity of Lough Foyle until we had established our claims on the lough and whether these extended to the high or low water mark.’