Work and Pensions Secretary Stephen Crabb is the first top Conservative to launch a bid to become the party's leader, as nominations open today (29 June) to become David Cameron's successor. Crabb, who was born in Scotland but brought up in Wales, will have the support of Business Secretary Sajid Javid and will run on a platform of "a plan for unity and opportunity".

Crabb and Javid both backed the unsuccessful Remain campaign in the EU referendum, but their back stories differ significantly from Old Etonians Cameron and Boris Johnson, the former mayor of London and Vote Leave campaigner who is also expected to run. Crabb, 43, was raised by his single mother in a Pembrokeshire council flat, while Javid, 46, is the state-schooled son of Pakistani bus driver.

Education Secretary Nicky Morgan, who is considered on the left of the party, revealed she was "actively considering" throwing her name in the hat when she appeared on BBC Radio 4's Today programme this morning.

She said the Tories needed to make a "positive case" for immigration after the UK voted to split from the EU in a 23 June referendum.

Home Secretary Theresa May is also expected to make a bid. May, 59, backed the Remain campaign ahead of the historic ballot, but argued that the UK should quit the European Convention on Human Rights. May's political positioning could make her the "stop Boris" candidate in the leadership election.

Meanwhile, Environment Secretary Liz Truss and Sir Nicholas Soames, Winston Churchill's grandson, are just two of the well-known names that have publicly backed Johnson. The Eurosceptic has not officially declared his intention to run, but he will have until noon on Thursday to do so. Johnson has the political momentum behind after his EU referendum victory.

However, he only recently returned to the House of Commons after being elected the MP for Uxbridge and South Ruislip at the 2015 general election. In contrast, May has been in Parliament since 1997, giving the Home Secretary the advantage when it comes to attracting support from the Conservative parliamentary party.

Elsewhere, Health Secretary Jeremy Hunt has hinted that he may run in the contest and Andrea Leadsom, the Brexit backer and former city minister, could boost Johnson's campaign after having a strong EU referendum campaign. If there are more than two candidates after nominations close on noon tomorrow night, Tory MPs will vote them down in consecutive rounds. The two candidates will then face off in a vote by the party membership.