rear body mount

Failed mot today, as sort of expected. Not to bad, three small bits of welding, No. plate light, Track rod end. One of the bits of welding needed is the rear body mount. Unfortunately had to murder the bolt to get it out. For something that was just hanging on it took some getting off. Anyhow, does anyone happen to know the size of the bolt required. I need to be finishing this job tomorrow as after that I have no time off for a few weeks.

TIA Dave