Online retail giant Amazon has announced that it has invested in human cloud food courier Deliveroo, BBC News reports. The exact figure was not given, but Amazon is the biggest investor in Deliveroo's latest round of fund raising, which in total raised £450 million. Deliveroo said it would use the money for international expansion, improving its service and to grow its delivery-only kitchens business. Several existing US investors also contributed to the fund raising. The company does not employ its riders directly, but pays them per delivery. Last year, a group of 50 UK Deliveroo couriers won a six-figure payout in a settlement over employment rights. The riders argued that they had been unlawfully denied rights, including the legal minimum wage and paid holiday, after being categorised as self-employed contractors.