This is a pleasant and surprisingly rural walk along the King Charles III Coastal Path as it winds its way along the North side of Portsmouth Harbour. Less muddy than many walks at this time of year, the route takes in Portchester Castle and in clear weather offers fine (though distant) views of Portsea Island. About a third of the route is on hard surfaces with much of the remainder on gravel tracks. The start of the walk has been timed to allow those wishing to come by train from Chichester to get the first off-peak service (9:05 arriving Portchester 9:33) at a return fare of less than £8 (with Railcard).
Note that there are no toilets at Portchester Station, though facilities are available at the end-point (ie Fareham Station). That said, there are a couple of intermediate locations where discreet toilet stops are possible. Along the way we will break for coffee/lunch (bring your own). Lunchtime refreshments are of course also available in the centre of Fareham.
Those desperate to arrive by car can usually find (free) on-street parking in Newtown, a few minutes walk from Portchester station.