If you can’t get the BBC iPlayer to work (I’m not sure it works outside of the UK; I thought it did), you can access this one via iTunes
- Pliny’s Natural History | In Our Time (iPlayer)
- Itunes link (I think this will take you there)
Podcast: Pliny the Elder on In Our Time
rogueclassicism 
The iPlayer usually works internationally for radio; however, there is a foolproof method: each In Our Time programme is downloadable in MP3 for a week after broadcast, so simply go to (and bookmark) http://www.bbc.co.uk/podcasts/series/iot