The two-tier cake was six metres high, making it taller than a double-decker bus. It was complete with 20 candles, which lit up at night.
The cake embarked on its maiden voyage at Stratford and floated along the river to Battersea and back over the course of the day. The cake concluded its journey at 8pm when it travelled between Waterloo and Blackfriars Bridge.
The stunt forms part of the online retailer’s month-long 20th anniversary birthday celebrations.
Other brand's taking to the Thames recently: