Short answer: Dogs are welcome on a lead in the castle grounds. The climb to the top of the keep is steep steps with no lift — fine for most dogs, harder for older ones. Around an hour for the whole site.
Launceston Castle sits right in the middle of town, and as an English Heritage site it follows the usual pattern — dogs on a lead across the grounds.
The walk round the grounds and up the motte gives genuinely panoramic views — you can see clear across into Devon on a good day. That's the main attraction, and it's fully available.
Getting to the top of the keep means steep steps with no lift. Most dogs manage fine; an older or less mobile one might be better staying at the lower level, where the views are still good.
There's no dedicated castle car park, but Launceston has several within a short walk, some with free short-stay periods.
Lawrence House museum nearby is free and dog-friendly on a lead — genuinely unusual for a museum — which makes a decent pairing on a wet day.
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