2FOR1 London offers – Galleries and Museums

Note that there can be multiple Railcards selected, and a number value (Number of Passengers with Selected Railcard) must be sent for each one selected.

The way it works is all selected "Railcards" are sent as a comma-delimited list in the rc field, and all the "Number of Passengers with Selected Railcard" are sent as a comma-delimited list in the rcc field which matches the order of the Railcards in the rc field.

So if there are two "16-25 Railcards" and one "HM Forces Railcard" it will be sent as:

            rc: "YNG,HMF"
            rcc: "2,1"
        

Also note that WebTIS doesn't handle Railcards very well, so this might not work well anyway. :(