They said three horses were believed to have run out onto the road from an adjacent field. After the accident one was taken away, by vets, with a suspected broken leg.
Police said noone else was injured.
The road was closed for about an hour for recovery work and re-opened at around 5pm.
• There was a similar incident involving horses three years ago on A26 between Uckfield and Lewes at Clay Hill when an Uckfield family considered themselves lucky to be alive after a horse smashed into the front of their vehicle.
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