"We're leaving the EU and because we are leaving the EU, we will be leaving the single market and by the way, we will be leaving the customs union".
Central to her attempts to govern effectively will be the more pro-European politicians in May's government.
But after a generation of discord over Europe inside her party, May's future could depend on her ability to please both the eurosceptic and pro-European factions in her party. She will not take part in day-to-day negotiations but is expected to set Britain's approach and have the final say on any compromises or concessions.
The newspaper quoted another former minister as saying: "If she weakened on Brexit, the world would fall in. all hell would break loose".
The other 27, including lead powers Germany and France, want to dissuade others from emulating Britain and so insist that any Brexit deal must be less advantageous than full membership.
The Queen's speech was due to be delivered on Monday but has been delayed to give the Tory minority government more time to strike a deal with the Democratic Unionist party.
She is also trying to contain outrage at home over a London tower block fire which left at least 30 people dead.
The ardent pro-EU leader echoed the remarks by German Finance Minister Wolfgang Schäuble earlier in the day that if the British wanted to come back, "they would find open doors".
"We've set out the broad principles from where we will start the negotiation and we will negotiate in good faith, but it is a negotiation and we recognise there will be an exchange of views and we will take that forward in a spirit of genuine cooperation", Chancellor of the Exchequer Philip Hammond told reporters in Luxembourg on Friday.
The talks, which kick off on Monday, will centre on Britain's divorce bill - which could be as high as £100billion - the status of expats and the Northern Irish border.
Three days after the talks begin, May is due to travel to Brussels for an European Union summit - a chance for the other 27 leaders to take stock of their negotiating partner in the sharply altered climate brought about by the dramas of the past two weeks.
There are also differences over the other priority issue for Brussels - securing the rights of three million European Union citizens living in Britain - but diplomats see those as less problematic.
And the source told the BBC that it was understood the talks would broadly follow the EU's preferred sequence, dealing with issues of citizens' rights and a framework for calculating outstanding financial liabilities before moving on, possibly later in the year, to deal with the UK's future relationship with the EU.
The arch-federalist former Belgian PM, who this year published a book calling on EU states to forge "a more ideal Union", warned last week Britain could lose its rebate and opt-outs if it changes its mind and decides to stay.
The Commission said the high-priority issue of the shared border between Northern Ireland, which is part of the United Kingdom, and Ireland, an European Union member, will also be discussed.
The Sunday Times said ministers within May's cabinet had "let it be known" they would oust the prime minister if they thought she could not pass the government's legislative program in a vote expected on June 28.style="text-align: center;"