Realising that print media was already saturated with images of The Troubles he began to incorporate his own photographs into photomontage work, juxtaposing his monochrome photos with collected imagery from religious pamphlets, London tourist postcards and toy packaging.
[7] Many of these photomontages have lengthy, wry titles such as Sr. Faustina Appears In LondonNewry, Miraculously Preventing The Illegal Photography Of Members Of The Security Forces...[8] Throughout the 1990s Hillen found it increasingly difficult to get his works into exhibitions and galleries, which he suspects was due to anxieties surrounding the Northern Ireland peace process.
[9] One of Hillen's collages features as a frontispiece in Art from Contemporary Conflict by Sara Bevan published by the Imperial War Museum in 2015.
[14] The title comes from a quote by poet Seamus Heaney on Hillen's work; "The photographs are like black and white time machines that bring back the desolation and danger of the Troubles.
In them Hillen creates surreal hybrid images combining ancient monuments like the Giza pyramid complex with nostalgic idealistic scenes of Ireland from tourist postcards by John Hinde.
Hillen has worked in other media and art forms, including sculpture, video, illustration, performance, stage and graphic design.