What capabilities? A British tanker was captured by the Iranians not long time ago. They had a destroyer in direct proximity to intervene. What was their reaction? The destroyer fled!
You are mislead. The ship in question was a frigate, HMS Montrose and she was too far away to intervene. She did not “run away”. https://www.newstalkzb.co.nz/on-air/kerre-mcivor-mornings/audio/robert-patman-audio-reveals-british-navy-failing-to-stop-oil-tanker-being-boarded/#ath