We have conducted a search for the giant Pair Halo structures which are inevitably formedaround TeV sources due to interactions of very high energy gamma-rays with the ExtragalacticBackground Light (EBL). The resulting electron/positron pairs are Compton upscattered onphotons of the 2.7 K Cosmic Microwave Background Radiation to produce a second generationof gamma-rays which again interact with the EBL; thus an electromagnetic cascade develops. Ifthe magnetic fields on Mpc scales surrounding the central source are sufficiently strong (10−11G or more), electrons are effectively isotropised before interacting with radiation fields. In thiscase an extended halo is produced around the source. Using H.E.S.S. observations of ActiveGalactic Nuclei, including data from PKS 2155-304, 1ES 1101-232 and 1ES 0229+200, we havecompleted a detailed analysis of these sources. I will present and discuss the astrophysicalimplications of these results.