default partial alphanumeric_keys
xkb_symbols "basic" {
  // define a base layout to inherit
  include "gb"

  // AltGr + a → ä / Ä
  key <AC01> { [ a, A, adiaeresis, Adiaeresis ] };
  // AltGr + o → ö / Ö
  key <AD09> { [ o, O, odiaeresis, Odiaeresis ] };
  // AltGr + u → ü / Ü
  key <AD07> { [ u, U, udiaeresis, Udiaeresis ] };

  // AltGr + e → €
  key <AD03> { [ e, E, EuroSign, EuroSign ] };
};