A motor gun boat could defeat Trafalgar's sailing fleet

What is the cheapest later warship that could defeat both fleets at Trafalgar?

A Second World War British D-class motor gun boat is the suggested low-cost candidate. Its ammunition is judged probably sufficient despite a panellist's reservation.

The comparison asks for a ship that was cheap in its own period, rather than the earliest vessel able to defeat the Trafalgar fleets. Monitor and Merrimack are challenged on their ability to operate safely in the open water of the battle. Warrior could do the job but was expensive for her time, while a 1910 Town-class cruiser is another possible candidate. The preferred cheaper example is a Second World War D-class motor boat in gunboat configuration. A Liberty ship with a 4-inch gun is also considered capable, though more expensive than the smaller boat. Its suggested armament includes two six-pounders, four 20 mm Oerlikons, and Vickers machine guns. Tracer ammunition could start fires aboard wooden ships, while the six-pounders provide heavier shellfire. A panellist questions ammunition endurance, but the six-pounder supply is judged probably sufficient and the D-class gunboat remains the preferred example. Similar river craft raise further seaworthiness concerns.