Former taoiseach Bertie Ahern says the UK leaving the European Union is not just a loss to the EU, but also to Anglo-Irish relations.
Brexit will become official at 11 pm tonight, with the UK and EU then set to enter an 11-month transition period.
The British Prime Minister Boris Johnson has again said he wants trade talks to conclude within that timescale - although EU leaders have warned that not every aspect will be able to be agreed by the end of the year.
Speaking on The Hard Shoulder today, Mr Ahern said Monday will see the next phase of the Brexit process 'really kicking off'.
He observed: "Monday will really kick off the next round of this - [Michel] Barnier's document comes out on Monday.
"I think he will say the same thing again: that EU restrictions on state aid and regulatory standards will be in exchange for a far-reaching trade deal.
"I think the EU will say it has to protect itself from unfair competition and protect the 27 and the integrity of the single market.
"Boris wants a broad free trade agreement covering goods and services and cooperation in other areas. I think the people will probably get fed up of listening to this, but I think it will not happen without there being some sort of closeness with EU regulations."
Mr Ahern said the EU allowed Irish and British politicians to meet regularly through European Council meetings - pointing to his own time at the table with British leaders such as John Major, Tony Blair and Gordon Brown.
However, he also stressed that it wasn't limited to the Council - pointing out that the two countries also frequently cooperated in working groups and other projects in the bloc.
Mr Ahern observed: "The close relationship that was built up over 47 years with the British system, the civil service and the agencies... that ends at 11 o'clock tonight.
"That did help immensely to build Anglo-Irish relations... it helped to build the confidence of British-Irish relations. It helped the Good Friday Agreement and all the way back to the Anglo-Irish Agreement in 1985.
"There is no other structure... there is no other place that our people meet and gather.
"With the institutions in the North up again... we can build up [an] alternative - but it is not a substitute for the close working relationship at all levels that we've had for 47 years."
