On 25 June 1807, Tsar Alexander I and Napoleon entered an accord at Tilsit, one of the secret clauses of which entailed the joint seizure of the Portuguese fleet. This led Napoleon to send a large army into Portugal in October 1807, with a demand that Portugal should detain all British ships and sequester British property. This led to the departure of a Naval Squadron under Sir Sidney Smith to blockade the Tagus estuary. The squadron consisted of the Hibernia (120 guns), the London (98), the Foudroyant (80) and Elizabeth, Conqueror, Marlborough, Monarch, Plantagenet and Bedford (all78s).
