Upon receiving a Royal Charter to trade in the Indian Ocean from Queen Elizabeth I in 1600, the English East India Company (EIC) adopted a flag of red and white stripes (varying from nine to thirteen stripes in total), with the St. George's Cross of England in the canton. Such canton was later changed following the Union Act joining England and Scotland to form a single kingdom.
Sources: Wikipedia(en):Flag_of_the_East_India_Company | «Flags of The World» (FOTW) website:East India Company - EIC (United Kingdom)
Sizes: ensign W12 x L18 mm, mast flags W8 x L12 mm, jack W6 x L9 mm, pennant W4 x L48 mm.