No king was found inside Silbury Hill.
Debated. The hill is real. No one agrees why it was built.
Silbury Hill is in Wiltshire, in south-west England, near Avebury and Stonehenge. It is about 30 metres tall and about 160 metres wide, and it is made mainly of chalk dug from the ground around it. Work began in the Late Neolithic, in the 3rd millennium BC, likely in the last hundred years of the 25th century BC. It was not built in one go. It began as a small gravel mound, less than a metre high, perhaps using gravel from the River Kennet. It grew in three phases, and a ditch was dug around it. Tunnels were later dug toward the centre in search of a burial. No burial chamber was found.
The page says people still do not agree what the hill was for, or whether the last phase came soon after the others or centuries later.
https://www.ancient-origins.net/ancient-places-europe/monumental-and-mysterious-silbury-hill-005729