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.