Even buzzing Brighton and Hove had never seen anything like it.
A quarter-of-a-million people descended on the seafront on Saturday to witness the city's favourite adopted son, DJ Norman Cook, in action.
By 2pm the beach was full. a few hours later the entire city had ground to a halt.
One person died, one was critically injured and 100 were treated for crushing, cuts and broken bones.
The fact the casualty count at the end did not turn out much higher is little short of a miracle.
Emergency services were at full-stretch, A&E departments were in chaos and the bus and train operators struggled to cope with the numbers.
The police, paramedics and coastguards fought a valiant rear-guard action responding quickly to the growing chaos without losing their cool.
The fans, too, must be praised for recognising the potential for catastrophe and behaving sensibly while still enjoying themselves.
It is a shame that what was undoubtedly a fabulous evening will be overshadowed by the chaos that ensued.
What should have been a showcase event in Brighton's bid to host the next City of Culture has instead exposed many of its real weaknesses.
If the concert is to become an annual event, as Norman has suggested, it will need a lot more careful thought to ensure the same problems and dangers do not occur again.
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