Possible Clues:

• Ferry port in northern France
• Caught, unfortunately, outside one Channel port
• Caught, unfortunately, after one's infiltrated end of tunnel
• Mary Tudor said it would be found 'lying in my heart'
• Caught, by bad luck, around one ferry port
• City on the Strait of Dover
• French seaport on the English Channel
• Port was Mary's problem
• In La Scala, I swig port
• A ferry runs between it and Dover