Mystery echoes in an embassy garden in DC

Tucked away in the garden at the British Embassy in Washington DC, a mini "magic circle" was a head scratcher for all those who stood on it.
That included Stormont ministers Emma Little-Pengelly, Gordon Lyons. Even Secretary of State Hilary Benn was left confused.
Jayne Brady, the head of the civil service, had a go alongside a host of local business leaders and the travelling press pack, including yours truly.
Nobody could make sense of it.
Once you stand in the circle and speak, the sound sensation is hard to explain.
A mix of being in an echo chamber and being surrounded by a wall of sound.
But only those standing on the circle can hear it.
A mini amphitheatre suggested a cameraman, but with only five steps it was hard to believe.
We had the same educated guess from Jenny Pyper, Pro-Chancellor of Ulster University.
The mystery remained unresolved and it may be a question for the new Ambassador Peter Mandelson at the next St Patrick's Day breakfast.
The trip to the magic circle came at the end of a week in Washington DC packed full of political noise.
But much of that was predictable, unlike the noise which baffled us all in the embassy gardens.