A SHOWDOWN between Theresa May and Nicola Sturgeon over a second independence referendum may be cancelled because of the Westminster terror attack, it has emerged.

The Prime Minister and First Minister had been due to meet next week, as Mrs May conducts her ‘grand tour’ of the UK before triggering the Brexit withdrawal process on Wednesday.

They were expected to discuss Ms Sturgeon’s demand for a new referendum by spring 2019, a timetable Mrs May has ruled out, saying “now is not the time” given the focus on Brexit.

However Whitehall sources suggested it may be impossible for the two leaders to meet, as the Westminster attack has forced a rethink of the Prime Minister’s diary.

The meeting had been due to take place between Holyrood voting on Ms Sturgeon’s plan to ask London for the power to stage a referendum and Mrs May invoking Article 50.

But the Westminster attack delayed the Holyrood vote until Tuesday evening, just a few hours before Mrs May sends her historic letter to Brussels.

The Herald has been told the UK Government cannot delay Article 50 beyond Wednesday, as it is followed on Thursday by a White Paper outlining the Great Repeal Bill, and Westminster goes into recess for Easter on Friday

One UK Government source said "events" had impacted on Mrs May's diary and it might now be difficult to arrange a meeting with the First Minister before next Wednesday.

A Scottish Government source also said the attack could “impinge” on the plan.

Last week, Number 10 said the PM's visit to Wales on Monday was part of an "ongoing engagement with the devolved nations" ahead of triggering Article 50 and that it was part of a "series of visits around the UK," which would include ones to Scotland and Northern Ireland.