Possible Clues:

• Maritime rescuer
• It has a strong pull in the port trade
• Small vessel designed to pull ships
• A tower of strength at Southampton, say
• It may pull a barge
• Tower in every detail penetrated by disastrous bug
• Craft perfectly capturing upper-class country
• Unerringly squashes bug that's buzzing around tower
• A tout planned to go round Britain -- in this vessel?
• Small vessel used for moving ships