Crowds attending the "Heroes Return" event waved flags and cheered when athletes such as gold medallists boxer Nicola Adams and gymnast Max Whitlock took to the stage in the central London square.
"Team GB" won 67 medals in Rio de Janeiro, including 27 gold, coming in second in the medals table after the United States. The "ParalympicsGB" team won 147 medals, including 64 gold, and came in second after China.
"Team GB and ParalympicsGB, you smashed it," London mayor Sadiq Khan told the athletes at the event. "We are now a sporting superpower."
On Monday, the athletes took part in a street parade in the city of Manchester. They will meet members of the British royal family at a reception with Queen Elizabeth and her husband Prince Philip later on Tuesday.
(Writing By Marie-Louise Gumuchian; Editing by Angus MacSwan)
