London will host the finishing parade of the Clipper Round the World Race as a 12-strong fleet of yachts marks a complete journey around the globe.
Thousands of friends and family of the crew members who set sail from Den Helder, Netherlands, on Thursday will line the River Thames and Tower Bridge to welcome them into port on Saturday.
As the fleet began the final sprint home, Clipper race founder Sir Robin Knox-Johnston, 77, described the 10th edition of the biennial event as "extremely tough".
The first person to sail solo non-stop around the world in 1968-69, he said: "The conditions encountered in the Pacific were the worst we've seen in 20 years of running the race.
"I am proud of all of the crew; they have taken on all the world's most challenging oceans and have been very resilient. They should be justly proud of themselves - whether crossing a single ocean or circumnavigating the entire planet.
"It is a remarkable achievement. The novices who set out 11 months ago have returned as seasoned sailors.
"This is the second outing of our third generation Clipper 70 fleet of ocean racers and they have proved themselves as sturdy and reliable in extreme conditions.
"In addition, the teams on this edition of the race have sailed particularly hard, which has resulted in some very fast times and tight finishes.
"It has gone down to the final sprint in this 14-race series to determine the podium and overall positions."
Dutch naval ships saw the crews out of port, with training vessel the Urania firing a cannon to officially launch the race.
With just six points separating the top two crews, the boats set sail across the North Sea, and will have to navigate past a number of oil rigs over the 30-hour journey to the official finish line at Southend Pier.
The procession is expected to pass the Thames Barrier at around 8.50am, Canary Wharf at 9.30am, Tower Bridge at 10am and into St Katharine Docks at 10.40am.