Adrian, Marcus, and Octavio are recent university graduates flat sharing in London. Each of them holds an individual bank account with NatEast Bank plc. Adrian is keen to start his own business (a shop specialising in comic book superhero paraphernalia). He requested a loan of 30,000 from NatEast but the bank manager told him that, given his poor credit score, he needed to provide some security for the loan to be approved. Adrian has no substantial assets but is aware that Marcus, who has a well-paid job in the entertainment industry, owns an expensive car. So, Adrian asked for Marcus's help and Marcus agreed to "help him deal with the admin" provided he would not actually have to pay anything out of his own pocket. Adrian and Marcus returned to NatEast. Adrian entered into a business loan agreement with NatEast whereby Marcus agreed to act as guarantor and secure any debts arising from the guarantee with a fixed charge on his car. Marcus signed the paperwork without fully appreciating the meaning of the terms "guarantee" and "fixed charge". A few weeks later, while Adrian was working hard to set up his business and, in doing so, had already spent most of the money he borrowed from NatEast, he was robbed of his mobile phone and debit card while walking on the street. Although he notified NatEast a few hours later on the same day, the robber had already made several purchases, using the contactless functionality of the card, totalling 500. To date NatEast has not reimbursed the money. This brought Adrian to a tight financial position as he needed to pay suppliers for his shop. Adrian knew that Marcus, who very occasionally checks his banking balance, keeps his online banking passwords in a notebook that he hides under his mattress (he discovered this by chance at a time when Marcus was out), and that he has no PIN on his phone, and never locks his bedroom door. While Marcus was taking a long shower, Adrian logged onto Marcus's online banking, using the password from the notebook and Marcus's phone to complete the two-stage authorisation process. He transferred 2,000 from Marcus's current account into his own account. His intention was to return the money before Marcus noticed. After a month, Marcus discovers the payment made out of his account and is furious against Adrian who in the meantime has spent all the funds. At the same time, Octavio had some payments refused and when inquiring with the bank he was told that his account "has been blocked for reasons that we are unable to disclose". Octavio has recently received a substantial amount of money from a Russian financial institution because he inherited the money from an uncle of his who lived in Russia and sadly passed away. Advise Adrian, Marcus, and Octavio on the legal issues arising from the above facts, from a banking law perspective, making reference to relevant legislation, regulatory rules and case law

Please help with this practice question.