light in the sky splits into 3, one of which is observed to be a huge triangle

Whilst I was waiting for a lift on a slip road to the M4 motorway, I spotted a light moving low on the horizon to the west. It went from left to right. I was looking out for a car, so I kept glancing at it until, all of a sudden it split into 3 lights one went back the way it had come, one carried on the way it was going and the third appeared to go straight up. The sun had just gone over the horizon and there was a little after glow in the sky. My attention switched to the light that was going upwards and I rialized that it was going to pass over me. As it got higher and closer I saw that it was a huge triangular craft with one light at the front. It passed over me silently [as far as I could tell]. Noone else saw it and it disappeared to the east in the direction of Cardiff.
We would be surprised if the date is accurate, although the witness indicates that it is exact.  One of three reports from same source.  PD