Harwich is around 90 miles (145km) from the centre of London. On a good day, a vehicle will make it in under 2 hours.
Harwich is the smallest of the three main cruise ports that serve London, (Harwich, Southampton and Dover).
It is a single berth, single terminal affair which, even at the height of the summer season, will only have a cruise ship every other day at its busiest time.
Next door to the cruise terminal is a ferry terminal with large ferries going to the Netherlands and Scandinavia. Both ferry and cruise terminals are a small part of a much larger port complex. On the other side of the river from Harwich is Felixstowe, one of the UK's largest container ports.
The only public transport option that runs on a scheduled basis daily is the train service. You will need to get to London's Liverpool Street Station where broadly hourly trains make the journey to Harwich International, adjacent to the cruise and ferry terminals. You will have to change trains at Manningtree Station as Harwich is on a branch line from the main London railway.
Unfortunately, Liverpool Street the London terminus of the trains from Harwich is not near where most people's hotels will be in Central London and is on the far side of London from Heathrow Airport, London's main airport.
There is a broadly hourly train between Harwich International Station and London's Liverpool Street Station. The Harwich line is a branch line and for nearly all train journeys between Harwich and London you will have to change trains at Manningtree Station. Journey time is around 75 minutes.
Note: Liverpool Street Station is in the City of London in the financial area of London, the other side of town from where most people will have their London hotel.
The London Underground or a 15-20 minute taxi ride is a tedious add-on to most people's journey.
Direct transfers between Harwich and London by private hire vehicle save a lot of hassle and tedium associated with the public transport alternatives.
It's around a 2 hour journey into London from Harwich. With most cruise ships disembarking between 7am and 9am if you are travelling on a work day, you'll hit a lot of commuter traffic and it can take far longer.