Explorer Will Millard usually visits locations as exotic and far-flung as Papua New Guinea, or involve feats such as rafting along the Mano/Moro river on the Sierra Leone and Liberia border.
However he admitted that visiting the Cardiff nuclear war bunker shown to him by Liverpool historian Jon Hogg was ‘definitely as scary as it gets’.
Jon has explored these bunkers, now abandoned by the Ministry of Defence, as part of his research on British nuclear culture.
You can find out more about Jon's visit to the bunkers in the BBC Wales programme ‘Hidden Cardiff with Will Millard’ on iPlayer.