The former secretary general of the European Commission, Catherine Day, has said it is politically desirable to have a longer period of time to negotiate the exit of the UK from the EU.  

Catherine Day, a special advisor to EU Commission President Jean Claude Juncker, said that a negotiating period of longer than two years is provided for in the EU treaties.

But she said that she did not expect Britain to seek an extension immediately, as it is not yet ideologically ready to make the kind of compromises needed to ensure a smooth and easy process for leaving the EU. 

Speaking at an event organised by the Alliance of Liberals and Democrats in Europe - the political family of a number of centre parties in the EU, including Fianna Fáil - the former top Eurocrat said Brussels is ready for the Brexit negotiations.

But Ms Day said that Britain has yet to make up its mind on where it is willing to compromise.  

She said that at the moment it is saying it wants everything - but for that you have to be a member of the EU.

"I think it's encouraging that people in the UK are focussing on what its all going to add up to," Ms Day said. 

According to Ms Day, the EU is very open to all sorts of arrangements, but added that every arrangement has a price.

If the UK wants to be in the single market it has to accept free movement, and if it wants to be in the customs union it can not negotiate its own trade agreements with anyone else, she explained.

"Everyone is waiting for the UK to get down to the nitty-gritty," she stated.

Ms Day said that she believes the start of the Brexit talks on Monday will focus on procedure and not substance.

The Commission has put up two papers on its website on citizens and finance and would expect the UK to respond, she added.  

The EU has also set out sequencing for the talks rather than just going to what the UK wants to talk about - the relationship after leaving.

Ms Day said that on migration, partial access can be agreed, but the UK has to say what it wants and so far it has not done this.

She said that we have to plan for the worst - Brexit is happening, but as someone who would like to keep the UK in the EU it would be good to keep an open door.