Jailhouse Cafe. Tough to find, but worth it for the view. 

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Jailhouse Café The Verne, on Portland, is fully open to the public and serves café food. Situated through IRC The Verne’s tunnel at the top of Portland, in the heart of the World Heritage Site, the café enjoys panoramic views over Weymouth Bay, Portland harbour, and all along the Jurassic Coast.

Jailhouse Café The Verne, Portland, is run by Expia, a charitable company, and staffed by risk assessed prisoners on day release. 

During the Summer, open every day, Monday to Friday and Weekends. Light refreshments between 10am and 3pm and hot meals between 12 and 2pm.