However, It's much more likely that what he actually saw were Noctilucent clouds.
These clouds resemble thin cirrus clouds but are usually bluish or silvery, sometimes orange to red, or reddish when on the horizon.
Thanks to Luke Johnson for this stunning image, photographed over Haverfordwest:
They are rare but can sometimes be seen on clear midsummer nights after sunset and appear to be more brilliant after midnight.
It's believed these clouds actually consist of ice crystals and they hover on the edge of space, about 80km (50 miles) above the Earth.
Noctilucent means 'shining at night', and that's exactly what these clouds do!