Uhm. British government regulations are that singers and musicians stand three meters apart, or (for singers) back-to-back, or side-by-side (in other words, not in rows on risers). “If the chorus at the Last Night of the Proms had to stand side-by-side then Rule Britannia would begin in the Royal Albert Hall and stretch all the way down to the Natural History Museum, almost half a kilometre away.” Also, again, it may not be safe at all. – BBC