The parcel went to a neighbour. Three weeks ago.

The tracking says delivered. Three weeks ago. To a neighbour who's never heard of it. This drafts a formal complaint to the retailer stating the order was marked delivered but never reached you, citing the Consumer Rights Act 2015, your contract is with them, not the courier, and demanding redelivery or a full refund within fourteen days.

Draft a formal complaint to [retailer] stating that [courier] marked my order [order number] as delivered on [date] but it never reached me. Cite the Consumer Rights Act 2015: the contract is with the retailer, not the courier. Demand redelivery or a full refund within 14 days.