<sod >Senior counter-terrorism officers are reported to be gathering in London following the explosion which occurred at the Manchester Arena at around 10.40pm at te end of a concert by pop star ArianaÂ Grande.< eod>< sod > Senior counter-terrorism officers are understood to be gathering in London following the explosion, which occurred at the Manchester Arena at 10.33pm, at the end of a concert by pop star Ariana Grande.< eod>