This is a glimpse into the private life of HM we see very rarely.
From the above article:
With a head- scarf to keep coal dust and smoke out of her hair - and a beaming smile - the Queen appeared as much a steam enthusiast as the driver, her friend Leopold de Rothschild. The Queen travelled to Exbury Gardens, in Hampshire, which is owned by the Rothschild family, for a private ceremony in which she named her friend's new train.
With a little curtain-unveiling no less!