Described as a dark, fat little man of about 60, he had large black handlebar moustaches and a cast in one eye. His typical modus operandi was to approach unsuspecting English tourists in Nice and ask them to bring a parcel back home with them and post it on their return. The parcels went to an accommodation address at the tobacco shop of Otto Cermak at Tottenham Court Road. His accomplice, the Contessa, would then collect the parcels under her false name of "Mary Jones". In this way, valuable jewels and even the proceeds of thefts could be smuggled into Britain without the need to pay duty.
Barrosa approached Alice Hall while she was staying at the Hotel Ruhl in Nice to run one such errand for him, rewarding her with a handbag. Unfortunately for him, Alice met Biggles and told him all about it, although she didn't know there was anything wrong in it at the time. Alice was also able to provide an accurate description of Barrosa. Biggles was able to identify Barrosa from Scotland Yard files.
Gaskin and Marcel Brissac subsequently mounted a sting operation for Barrosa using a British policewoman posing as an English tourist at the Hotel Ruhl. Barrosa was spotted handing a parcel to the woman and arrested. The parcel turned out to contain jewels which had been stolen from a jewel raid in the South of France. The policewoman brought the parcel back to England and posted it to Cermak's as arranged. The Contessa was then arrested when she turned up as Mary Jones to collect the parcel.