Composer Stephen Sondheim will create the challenge as part of a gala to raise funds for the Friends In Deed charity on 3 October (11).

The A Little Jurassic Treasure Hunt event will mark the 20th anniversary of Friends In Deed, which aids those suffering from life-threatening illnesses.

After a cocktail reception and the treasure hunt, thespians Barbara Cook and Raul Esparza will perform Sondheim's songs during a dinner reception.

The composer is a wily treasure hunt fan and has devised private treasure hunt parties for friends for decades.