Last year The Tim Traveller created an excellent video about the last remaining Hoverport from the halcyon days of cross channel Hovercraft operations - at Boulogne-sur-Mer.
Tim's video spurred the thought - would it be possible to do a day trip from London to Boulogne?
The easiest option would be to drive to Folkestone, take Le Shuttle, and drive straight to Boulogne.
But what about travelling without a car ... going by train to Dover ... and ferry Calais ... and train to Boulogne ... is that feasible?
Train to Dover
In order to make the 10.40am DFDS ferry (see below) you'd need the 7.10am train from Victoria (arriving Dover Priory 9.09am) or the Javelin departing St Pancras at 8.07am (arriving Dover Priory at 9.12am).
In order to make the 11.30am P&O ferry (see below) you'd need the 7.29am train from Victoria (arriving Dover Priory 9.31am) or the Javelin high speed departing St Pancras at 8.07am (arriving Dover Priory at 9.12am).
Ferry to Calais
Unfortunately there's only three P&O ferries a day which take foot passengers - with departures from Dover at 9.45am, 1.40pm and 4.40pm. P&O also have a 90 minute checkin deadline, so with the port being a 20 minute taxi ride from the station (or 30 minutes walk downhill or a 15 minute cycle), you'd need to get into Dover Priory by 7.45am / 11.40am / 2.40pm to make the checkin cutoff.
However, if you're on a bicycle all the P&O sailings become available, including the 11.30am departure (getting into Calais at 2pm) - and cyclists also benefit from a more civilised 60 minute checkin requirement.
Irish Ferries do not accept foot passengers or cyclists across the Channel. Thankfully DFDS do allow cyclists (but not foot passengers) on their services, including the 10.40am departure which arrives into Calais at 1.20pm with their slightly longer sailing time.
Train to Boulogne
Getting from the Port of Calais to Calais Ville station takes about 15 minutes by taxi, 20 minutes by bus, 15 by bicycle or half an hour walking.
The train from Calais Ville to Boulogne-sur-Mur takes just 27 minutes, with the slower service taking 32 minutes but delivering you into the centre of Boulogne at the Tintelleries station. The Calais Frethun service (as well as being 10km out of town) uses a TGV trainset. Trains operate every couple of hours.
Cyclists can bring standard bicycles on regional trains in the Haut France region without a reservation between start of November and the start of May (subject to space).
The Velo A Bord website from SNCF confirms that no reservation is needed until the end of April.
Getting from Boulogne-sur-Mer station to the old Hoverport takes about 45 minute walking, or 12 minutes cycling or 6 minutes in a taxi.
With the two hour gap between trains, on Saturdays the last train back from Boulogne to get to Calais in time for the 8.10pm ferry (see below) departs Boulogne soon after 5pm, arriving into Calais Ville just after 5.30pm. On weekdays there's departures around 5.27pm and 6.13pm which get into Calais Ville with enough time to catch the 8.10pm ferry.
Back to Blighty
The last P&O ferry which takes foot passengers departs Calais at 7pm arriving into Dover at 7.30pm - so you'd need to be at the port in Calais to check in by 5.30pm.
Cyclists have extra P&O ferry options including the 8.10pm departure (arriving 8.40pm) and the 10.25pm departure (arriving 10.55pm) - with a normal 60 minute checkin time.
Cyclists also have the option of DFDS ferries including their 6.05pm departure (arriving 6.45pm), the 7.35pm departure (arriving 8.15pm) and the 11.10pm departure (arriving 11.50pm) - also with a 1 hour checkin deadline.
London bound
Getting to Dover Priory station from the ferry terminal takes about 10 minutes in a taxi, 15 minutes on a bicycle or something over half an hour on foot.
On Sundays the last departure for London is before 10pm. On weekdays the last Victoria departure is around 9.45pm with the 10.45pm high speed Javelin departure the last of the day.
Pricing
Taking Le Shuttle for a day trip can cost around £100 for a car and up to nine passengers if booked in advance. If you wanted to travel tomorrow it would cost £148 plus fuel costs.
Taking the ferry, either as a foot passenger or on a bicycle, costs around £50 for the return journey. The return train from London to Dover is around £30 with a Network Railcard. And the return train from Calais to Boulogne about £17.50 giving a total of nearly £100 per person.
Conclusion
Since there aren't any trains from London that get into Dover in time for the 8.15am morning sailing checkin deadline - it is not possible to do this daytrip as a foot passenger.
Taking a bicycle opens up more ferries, with 8.07am Javelin from St Pancras connecting nicely with the 10.40 DFDS ferry, arriving at 1.20pm into Calais.
Taking the 2.34pm train from Calais Ville you would have a couple of hours in Boulogne before getting the 5.08pm service from Boulogne back to Calais.
Departing Calais on the 8.10pm P&O or the 7.35pm DFDS ferry would get into Dover in plenty of time to catch a train back to London.