Ukip's Steven Woolfe is spending the night recovering in a hospital in Strasbourg after being admitted in a "serious" condition following what Nigel Farage described as an "altercation" at a meeting of the party's MEPs.
If you're wondering who he is, here are 11 things you should know about the party's leadership favourite.
1. He's a 48-year-old barrister, who is of mixed race and was born and brought up in the North.
2. He's regarded by many within Ukip as a candidate able to broaden the party's appeal beyond its southern and middle-class core.
3. He has been the party's MEP for North West England since July 2014.
4. He was the Ukip candidate for Labour-held Stockport in 2015, where he finished third with 13.1% of the vote.
5. There were signs he could be a front-runner to succeed Nigel Farage, even before the election, when the party suggested he stand in a live TV debate after Farage pulled out for "family reasons" (though Channel 4 denied the request).
6. He was tipped to win the recent leadership contest before he was barred for submitting his nomination papers 17 minutes late, blaming it on technical difficulties. Supporters claimed it was part of a coup led by Ukip's only MP, Douglas Carswell, and Neil Hamilton, group leader in the Welsh Assembly.
7. He was embroiled in controversy earlier this year when it emerged he had admitted failing to declare a drink-driving conviction when he stood for a police and crime commissioner post. He said he "forgot about the conviction" when he stood in the Greater Manchester PCC election in 2012 - which is actually a possible breach of electoral law - but police said he wouldn't face any action.
8. He was the first leadership contender to throw his hat in the ring following the shock resignation of Diane James this week.
9. His personal website says he was born on October 9 1967 in Moss Side in Manchester, and grew up in Burnage as the eldest of a family of four.
10. He went to school at St Bede's RC Independent College and later studied law at Aberystwyth University before beginning his legal career at chambers in Inner Temple.
11. Prior to politics, Woolfe worked as a lawyer in the City of London and acted as counsel for hedge fund managers, as well as a consultant to financial institutions.