After a three-year break travelling to Mexico and founding an English language school, Gillespie returned to the UK and began an apprenticeship in restoration and conservation of fine art paintings.

The conservation treatment carried out on paintings as part of this TV programme has resulted in the re-discovery of previously lost or unknown masterpieces, including: The most significant discovery arising from Gillespie's work on the show Fake or Fortune?

(with Philip Mould and Fiona Bruce) was in 2015, when a Pietà from St John the Baptist's Church, Tunstall in Lancashire was revealed to be by the Italian painter Francesco Montemezzano.

[14] Philip Mould said of the result of Gillespie's conservation treatment: “It was an extraordinary transformation and on a scale that is pretty well unmatched.

[23][24][25][26] The picture, depicting David with the Head of Goliath and belonging to a private collector who brought it to Gillespie's studio for treatment after purchasing it at auction in December 2018, was published in an article written by Gianni Papi in The Burlington Magazine.