Studio Mug, dp mark and HF mark

Can't remember if I've already posted this (apologies if so).

Studio mug with two seals under the handle. The upper looks like the Greek Phi symbol with a longer stick and the lower looks like HF. Any suggestions appreciated.

The HP is probably Haverfordwest pottery. Anne and Theodore Whalley who producee tableware ans stoneware 1962-69. The pieces I have seen have always been of a very good quality. The other mark I don't know, probably another potter who worked there.

But it might be HF
Haverfordwest‘s HP mark. And Paul Whalley usually signs his pieces
https://pin.it/60Tf9v3

I'd have to agree with Naomi, there's no loop for the P so would put money on it being an F. I'd tend towards the upper mark being for the pottery and the lower for the potter.