The EU will vow to act “as one” to minimise the damage caused by Brexit on the rest of the bloc, according to a leaked draft of the joint statement which will be issued in response to Britain triggering Article 50.

Donald Tusk, as President of the European Council, will deliver the statement after the EU formally receives Theresa May’s notification letter, at around 12.30pm BST.

According to a leaked version seen by the EURACTIV website, the European Council will emphasise the need to reach a comprehensive divorce deal before any discussions of future trade can begin.

Theresa May announces the triggering of Article 50

Mr Tusk will say the EU’s first priority is to “minimise the uncertainty caused by the decision of the United Kingdom for our citizens, businesses and member states”.

“Therefore, we will start by focusing on all key arrangements for an orderly withdrawal,” the statement will say.

The statement will also stress that, while the EU wants to have a positive trading relationship with the UK in future, it is “ready” to walk away from talks.

“We will approach these talks constructively and strive to find an agreement. In the future, we hope to have the United Kingdom as a close partner,” Mr Tusk will say, according to EURACTIV.

He added that should the negotiations fail, the Council would make sure that the “European Union is ready for such an outcome even though we do not desire it”.

On Wednesday morning, Theresa May gathered her senior ministers for a special one-hour cabinet meeting in Downing Street.

The Prime Minister signed the letter that starts the formal exit process on Tuesday afternoon, and the senior diplomat Sir Tim Barrow has arrived in Brussels to deliver the historic document by hand.

Shortly before the cabinet meeting, Chancellor Philip Hammond said the letter sets the "right tone" and sends the "right signals" to European leaders about how the UK wants to conduct the negotiations that will decide the country's future.

At some time after 12.30pm, Ms May will inform MPs that Brexit is being triggered and, in Brussels, British ambassador to the EU Sir Tim will deliver the document to Mr Tusk.

Once it has been accepted, Article 50 will have been officially launched, starting a two-year countdown to the UK leaving the EU.