There's a garden tap at our new house in the garden!

I've tried to attach our Hozelock 3/4" BSP adapter but
it does not fit. The tap thread seems to be very slightly bigger.

The only markings on the tap's brass body is what looks like a
BS kite mark and the text 'No2'.

Any thoughts as to what size it might be and if I can get an adapter
for my Hozelock? The Hozelock will also attach to 1" BSP so a
'whatever my tap to 1" BSP' adapter would be ideal.

TIA

Guy