Expatriates who want to be allowed to vote in the European Union referendum are taking their case to the High Court.
They are urgently challenging restrictions which lawyers estimate are preventing up to two million Britons living in Europe from voting on June 23.
Those seeking a judicial review include 94-year-old Second World War veteran Harry Shindler, who lives in Italy, and lawyer and Belgian resident Jacquelyn MacLennan.
Both claim that under the EU Referendum Act 2015 they are being denied the right to vote on the UK's continued membership of the EU, having lived outside the UK for over 15 years.
Mr Shindler, who retired to Italy in 1982, has previously said the legal challenge was the ''last stand'' for expats who fear for their way of life if the UK severs ties with Brussels.
The veteran, who will not be at London's High Court for the hearing, said he would vote Remain if he had the chance as many expats were concerned about the future if the UK voted to leave.
''It would have very serious repercussions for all expats and their families here,'' he told the Press Association recently.
''I came here in 1982 when you had to have a permit from the police to stay here. All that would come back. We would be immigrants here.''
Mr Shindler, who fought in Italy during the Second World War and was part of the Anzio landings in 1944, said younger expats could be forced to apply for work permits to remain in their adopted countries.
He was sceptical about assurances from the Leave camp that there would be little change in the status of Britons living in the EU following Brexit.
Ms MacLennan is planning to be in court along with Charlotte Oliver, an English lawyer based in Rome who runs her own practice in the Italian capital and who is supporting the legal action.
Lawyers for the claimants, who are represented by solicitors firm Leigh Day, will argue that excluding UK expats who have lived elsewhere in the EU for more than 15 years acts as a disincentive from, and a penalty for, their exercising their free movement rights as EU residents.
The judicial review of the legislation, if successful, should require the Government to rush through amending legislation to change the franchise for the referendum, according to Richard Stein of Leigh Day.
Mr Stein said: ''We believe that the Government has the time now to amend the franchise and empower the many expats who have lived outside the UK for over 15 years who want to vote on decisions which will have a very real impact on their lives.
''This legal action should not delay the referendum, the Government should instead stand by its promises and give a 'vote for life' to British citizens.''