My wife drew my attention to two two precisely similar balls of light directly overhead in Hampshire during July at midday when we were in the garden at lunchtime.
They initially appeared separately at about 3/4000′ in a clear blue sky. Other jet aircraft descending into both Heathrow and Bournemouth at a similar height had left vapour trails. The lights we witnessed did not and there was no sound. Jets at this height on let down are audible.
As a pilot I am very familiar with recognizing and identifying other airborne craft for safety reasons.
Whatever we witnessed perforrmed 6 to 8 slow circular rotations around each other. They then parted in opposite directions, on to the South East, the other to the North West.
Each increased their velocity after breaking their rotational formation slowly at first and then with extreme acceleration disappearing completely from view within 15 to 20 seconds.
Our regret was that we didn’t have an I phone, or pad outside with us on that occasion.