It replaced the Brexit Transition Agreement and restored Britain’s place as a fully independent trading nation. The UK withdrew from the European single market and stopped implementing laws passed in Brussels.
Home Vale de Almedia, the EU’s top diplomat in the UK, admitted there were still tensions between Britain and the bloc.
He said there remains a “lack of understanding” of what parts of the agreement mean.
Exports of some British agricultural products to the EU fell significantly after Brexit due to the imposition of new controls.
He commented: “Decisions have consequences and you have to be aware of them.
“What we need to distinguish are the temporary problems and the structural problems that will not go away with time, which are linked to the UK’s decision to leave the single market and the customs union.”
Some of the worst tensions have been over Northern Ireland, as the UK unilaterally decided to delay the introduction of some customs controls.
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“We are emotionally and politically engaged in Northern Ireland.
“We have been sponsors and supporters of the Good Friday Agreement from the start and we are always there and attentive.”
Dozens of French fishing boats protested off Jersey on Thursday after post-Brexit rules tightened access to the island’s fishing stocks.
Some small French vessels say they are unable to provide the evidence required by the British authorities.
Mr de Almedia played down the confrontation and insisted that it can be resolved diplomatically.
The Portuguese diplomat said: “This relationship should not be sidetracked by accidents or pushes.
Mr. de Almedia was recently granted full ambassadorial status by the government.
He initially refused, on the grounds that the EU is not a country, infuriating Brussels.