Hi Tom,
Thanks for the response.
As soon as I place the code you have given me in the functions file I do get the following error
Fatal error: Cannot redeclare generate_nav_dropdown() (previously declared in /home/XXXXX/public_html/wp-content/themes/XXXXXXX/functions.php:24) in /home/XXXXXXX/public_html/wp-content/themes/generatepress/inc/navigation.php on line 216
Any ideas?