Those 15,000-plus passengers on the seven ships, embarking to points across the world, had an extraordinary send-off (complete with ‘flutterfetti' and the pyrotechnics), but for those onshore and in small boats in the Solent, the event also proved memorable.
During the event, Cruise Critic reported live from a boat in the Solent, so check out all our coverage of the big day located below.
Slideshow: P&O's Grand Event
Despite the uncooperative British summer, P&O's Grand Event was a smashing success. See the top photos from the day.
Blog: Words from our Winner
What did our Grand Event contest winner think about her prize? Get the story in her own words.
Slideshow: P&O's 175 Years
P&O can trace its routes back to 1837, with the formation of the Peninsular Steam Navigation Company (PSNC). Ogle the vintage gallery.
P&O's Grand Event: What's Special
Wait -- didn't another venerable British line (Cunard) just stage a massive celebration? Here's why P&O's Grant Event will be different.
Southampton Preps for Huge Crowds
On 3 July, seven ships and some 30,000 passengers will descend on Southampton for an unprecedented event.
Poll: Best P&O Ship of All Time?
As we look back at P&O's amazing 175 years of history, we're wondering: What's your favourite P&O ship, past or present? Vote here.
Tonnage: 115,000 gt.
Tonnage: 116,000 gt.
Tonnage: 83,781 gt.
Tonnage: 30,200 gt.
Tonnage: 77,000 gt.
Tonnage: 76,000 gt.
Tonnage: 69,000 gt.