H. G. Muller wrote on Thu, Aug 17, 2017 10:47 PM UTC:
More generally 'en passant' (french for 'while passing') means that you capture a piece not on the square where it is, but on a square it passed through on the preceding move. In orthodox Chess Pawns can capture other Pawns en passant, and any piece can capture a King en passant (which, due to the rule that it is not legal to expose your King to capture, then means you cannot pass through check, and only applies to castling, as normal King moves never pass through anything).
In Caissa Britannia the royal piece does have normal moves that do pass through other squares.
More generally 'en passant' (french for 'while passing') means that you capture a piece not on the square where it is, but on a square it passed through on the preceding move. In orthodox Chess Pawns can capture other Pawns en passant, and any piece can capture a King en passant (which, due to the rule that it is not legal to expose your King to capture, then means you cannot pass through check, and only applies to castling, as normal King moves never pass through anything).
In Caissa Britannia the royal piece does have normal moves that do pass through other squares.