Five men have announced their intention to take over from Bob Crow as head of the Rail, Maritime and Transport union following the 52-year-old's sudden death.
Acting general secretary Mick Cash, closely involved in talks which prevented a 72-hour Tube strike, will stand as will London regional organiser John Leach.
The current assistant general secretary Steve Hedley, pictured holding an assault rifle on his Facebook page, is also among the candidates.
Other candidates include former union president Alex Gordon and Alan Pottage, the RMT's Edinburgh-based national organising co-ordinator.
Nominations for the job close in early July and the result will be announced in September.
Mayor of London Boris Johnson believes the aborted strike on London Underground was broken by commuter power.Read the full story ›
Londoners expecting to face the chaos of a Tube strike this morning can breathe a sigh of relief.
A last-ditch effort to avert the planned three-day strike was successful, with the announcement being made just hours before the industrial action was scheduled to begin.
London Underground bosses said yesteraday they are pleased with the result of the talks, but say more work is needed to resolve the disputes over the future of the Tube.
London Underground and the Rail, Maritime and Transport union have welcomed the decision to suspend a three-day tube strike, which was due to start tonight at 9pm.
I am pleased that Londoners will not have to endure further strike action this week. The only way to resolve this dispute is for the RMT leadership to work with us to shape the future of the Tube in a changing world. It is good that they have committed to doing so alongside the three other unions involved.
We have been able to secure real movement and significant progress on the issues at the heart of this dispute in talks with the Tube management over the bank holiday weekend.
The planned three-day strike by London Underground workers has been suspended, the RMT Union has said.
The London Underground and Rail, Maritime and Transport are holding last-ditch talks just hours before a three day strike, that could affect millions of people across London and surrounding areas.
Conciliation service Acas said the talks between the RMT and London Underground started at 10am.
RMT union members are set to walk out of their jobs for three days at 9pm this evening, in a long-running dispute with the London Underground over ticket office closures.
A two-day strike last week caused huge disruption, with roads clogged as people switched to other forms of transport.
London Mayor Boris Johnson claimed this evening that London is being 'held to ransom' by the RMT Union over next week's planned Tube strike.
His comments came as talks between London Underground and unions bosses finished today with the planned three day stoppage still on.
The Mayor said: said: "Once again London is being held to ransom by a minority of just one union, the RMT, who, unlike the other three unions, and on a ballot taken last November with just 30 per cent support, is digging in its heels and refusing to play its part in shaping the future of the Tube."
"Less than three per cent of journeys involve a visit to Victorian era ticket offices, which cost Londoners £50 million a year to run. It makes absolutely no sense to keep them open.
RMT said after "eight hours of talking about very little" next week's 72-hour Tube strike was still on.
"They have spent eight hours talking about very little so regrettably the strike is still on," the RMT's John Leach said outside Acas.
Next week's planned 72-hour Tube strike is still on after talks between London Underground management and the RMT union broke down.
Boris Johnson has claimed that an RMT member told him not to "give in" on the issue of ticket office closures on the London Underground.
London Underground management and RMT leaders are involved in talks at conciliation service Acas as they attempt to avert a planned 72-hour Tube strike next week.
"He said 'I'm an RMT member. Whatever you do don't give in.This is the right thing to do' - and that's what we're going to do," the mayor said.
The union staged a 48-hour strike earlier this week.