When an Algerian citizen in France on a French tourist visa wishes to visit the UK, entering and leaving by Eurostar, must he apply for a UK tourist visa?
If so, should he apply 3 months before (as if flying from Algeria to the UK) or is the UK tourist visa issued without prior application when he shows his French visa and Algerian passport to the UKVI at the railway station in Paris?
I am wondering whether he would have the option of deciding on the spur of the moment to get a train from Paris to London for a few days, or whether because of UK immigration laws his trip would need to be planned months in advance and at the cost of a second visa.