Royal Navy minehunters survey River Mersey
Royal Navy minehunters are carrying out a survey of the River Mersey as part of an anti-terrorist planning operation.
The UK-wide operation is surveying the country's harbours and their approaches.
The Hunt class minehunter HMS Brocklesby and the Sandown class HMS Grimsby will be in the Mersey until 24 November.
The survey information will update a database that will be used if any future operation needs to clear seaways and maritime infrastructure.