Newspaper headlines: Poll predictions, junior doctor talks and Leonardo da Vinci burial mystery

The first editions of Friday's newspapers were published as polls closed across the UK in elections to the Scottish Parliament, the Welsh and Northern Ireland Assemblies, and more than 120 councils in England.

Several papers, however, decide to speculate on the potential impact of the results on Labour, amid forecasts of losses.

The Daily Express reports that party leader Jeremy Corbyn was braced for furious calls for his resignation.

But, says the Times, grassroots supporters were preparing to fend off any challenge to his leadership. And the Daily Mirror says Sadiq Khan is set to spare Mr Corbyn's blushes as opinion polls indicate he will be crowned London mayor on Friday.

"Labour hopes win in capital will offset testing day nationwide," is the Guardian's take on the situation.

Ahead of the declaration of the mayoral vote, the Daily Telegraph reports the Conservatives are prepared to challenge the result in the courts in the event of a close win for Mr Khan over their candidate, Zac Goldsmith.

It follows chaos at polling stations in the borough of Barnet, north London, where thousands of people are said to have been turned away because officials were given incomplete lists of registered voters.

And with the votes in the Holyrood election being counted overnight, the early editions of Scotland's newspapers are predicting an SNP election victory and "five more years" for First Minister Nicola Sturgeon.

The announcement that talks are likely to resume between the government and the British Medical Association over a new junior doctors' contract in England is seen as a welcome development.

"At last," says the Guardian, "common sense, and maybe a revived awareness of their responsibilities to patients, has persuaded both the health secretary and the junior doctors to agree to another attempt to find a settlement in their painful and damaging dispute."

But the Guardian says doctors' leaders are split over a pre-condition that they commit in writing to discuss whether Saturdays should become part of a medic's normal working week.

The BMA must be willing to show flexibility, says the Daily Mail. "Like other trade unions, its first instinct is to regard any change to its members' working practices as an intolerable affront."

The Daily Mirror portrays the development as a U-turn by Health Secretary Jeremy Hunt after he had previously rejected calls for more talks. But the Sun believes Mr Hunt "has handled the junior doctors' militant intransigence with remarkable patience".

"US bans Britons with 'old' passports," says the Daily Mail's front page headline.

It reports on incidents of British families flying to the US who have been barred from boarding planes at the last minute because of a change to passport rules. An anti-terror law "quietly introduced" last month requires travellers to have the biometric passports issued after October 2006, says the paper.

"Travel agencies have been warning their clients flying to the US, but those travelling independently have been caught out since little effort has so far been made by airlines to warn passengers of the new visa requirements," reports the Guardian.

The Daily Mirror highlights the case of Vic Ryan, from Lincoln, who booked a holiday to Florida only to turn up at the check-in desk to be advised that he would not be allowed to travel. He spent more than £500 to resolve the issue and later flew out to join his family who had travelled ahead.

In other news, the Daily Express says freight industry bosses are warning of further disruption for holidaymakers and lorries at Channel ports this summer. The paper says truck drivers fear migrants are set to make fresh attempts to reach the UK as "stowaways", although it also highlights the efforts by the UK and French authorities to boost security at ports in northern France.

The Financial Times carries research by Oxford University's Migration Observatory which suggests three-quarters of EU citizens working in the UK would not meet current visa requirements for non-EU overseas workers if Britain voted to leave the bloc.

While the FT says the findings illustrate the scale of the challenges employers could face in finding staff in the event of Brexit, the Daily Mail reports Leave campaigners are likely to seize on the study as proof Britain is unable to control which workers it lets in.

The lead story in the the New Day, which is publishing its final edition just two months after it started, focuses on claims that some teachers in England are fiddling the results of Sats examinations. The teachers are said to feel under pressure to maintain their school's place in league tables.

The New Day quotes the Department for Education as saying it has improved methods for detecting "maladministration", but also carries a union's explanation that parents should have every confidence in the system because most of the issues can be put down to problems in administering the tests.

Meanwhile, in a letter to readers, the New Day's editor Alison Phillips pays tribute to the work of her "passionate, creative and gutsy" staff. "We tried everything we could but sadly we just haven't reached the sales figures we needed to make the paper work financially," she says.

The Times splashes on the news that Britain's biggest mortgage lender is to increase its age limit from 75 to 80. Many older borrowers have had difficulties in getting approval for a mortgage because of strict rules on lending into retirement but the Halifax will introduce the changes in response to "shifting demographics and working habits", says the paper.

"A 55 year old will be able to take out a 25-year mortgage as long as they prove they can afford the repayments," explains the Daily Mail, noting that there are now calls for other banks to follow suit.

The Daily Telegraph launches a campaign to ensure high-speed internet connections are available all over the UK amid reports the government has abandoned a pledge to roll-out the technology to every home, to save money.

A Culture, Media and Sport source is quoted as saying it "just makes sense" for links to the most remote places in the UK to currently be provided through a "request based" scheme.

Finally, the Daily Telegraph reports the mystery of where Leonardo da Vinci is buried could finally be laid to rest.

The artist and inventor was interred in the chapel of Saint-Florentin at the Chateau d'Amboise in the Loire Valley, in 1519 but the building was destroyed in the French revolution. Although it is believed his remains were reburied in the castle's smaller chapel, this has not been confirmed.

Scientists are hoping that advances in genetic testing could provide a definitive answer.

They believe Leonardo may have left traces of his DNA in paintings, notebooks and drawings, and specialists from the J Craig Venter Institute in California are expected to carry out tests on Adoration of the Magi, currently undergoing restoration in Florence.

The experts will compare any DNA found to living relatives, before testing samples from the grave in a similar way to how King Richard III was identified after his body was found in a Leicester car park, says the Telegraph.