It’s hard to tell since the graphic is in monochrome, but it is possible that the bottom flag is a “masthead” or “commissioning” pennant used by the (UK) Royal Navy.
“In the Royal Navy, the commissioning pennant has a cross of St. George in the hoist and a white fly. The pennant reflects the fact that the ship is a ship of war, and is flown until the ship is decommissioned. It is generally taken to signify the commissioned status of the warship. A boat carrying a captain of one of Her Majesty’s ships will on ceremonial occasions fly a commissioning pennant from the bows of the boat as a symbol of his authority as well. Modern Royal Navy commissioning pennants are significantly shorter than in previous centuries - typically 1m in length and only 10cm at the hoist, tapering to a squared-off point…field consists [of] white with the red cross of St. George sewn on at the head.”
Source: http://lighthouseantiques.net/Flags.htm. (Scroll way, way down.)
The top pennant could be showing the St. Patrick’s cross.
This website may lead you to useful info: http://www.crwflags.com/fotw/flags/gb^~pen.html