I think I've worked it out. The Song Thrush is a smaller, longer bird than the Mistle Thrush with less distinctive markings.
The Mistle Thrush stands very tall and has a pretty speckled chest.
I think the pair I saw in the park were Song Thrushes.
I haven't seen a Mistle Thrush for years but I have seen some Pied Wag Tails in the area.
Tommy Robinson arrested. Police using their existing powers