European Union citizens could remain free to move to Britain until 2021 under Theresa May's plans for a two-year Brexit implementation period in which Brussels rules and regulations will continue to apply.
Free movement of people under EU law will formally end on Brexit day, expected in March 2019, but the only major immigration control that will be applied to the bloc's nationals during the transition is a requirement to register with the authorities.
The move is designed to ensure "access to one another's markets should continue on current terms" for the time-limited period, despite the UK leaving the single market and customs union, raising questions over whether Brexit was being delayed in all but name.
In a landmark speech, Mrs May also pledged that other EU nations would not be left out of pocket by the UK's decision to leave, because it will pay budgetary contributions agreed in 2014 which run to 2020, paving the way for an estimated payment of around £18bn (around 20 billion euro).
Mrs May declined to put a figure on the amount the UK will pay in its so-called divorce bill and stressed the final total could not be agreed until the negotiations are settled.
But she insisted estimates of Britain's liabilities ranging from £50bn to £80bn were "exaggerated and unhelpful" as a Government source stressed there would be no payments for access to the single market or beyond the transition, although money could be made available for specific programmes, for example in science and research.
The address in the Italian city of Florence was designed to break the deadlock in Brexit negotiations and was described as "constructive" by the EU's chief Brexit negotiator Michel Barnier.
But he immediately raised questions, stressing that Brussels will assess whether the financial offer "covers all commitments" made by the UK as a member state, suggesting that more progress was needed before talks could move on to a future free trade deal.
Mrs May rejected pre-existing models for a future UK-EU relationship, describing a Norway-style membership of the European Economic Area (EEA) or Canada's free trade deal (Ceta) on goods as "unimaginative".
The PM assured EU nationals living in the UK that she wanted them to be able to "carry on living your lives as before", and said that protections for them would be written into UK law.