I recently found the following information posted on the internet:
"Captain Henry Hartwell was expected to head a settlement in the northern part of Maltravers’s county of Norfolk. What success these men had or what contributed to their failure cannot now be determined. Documents which might have answered these questions were burned in Richmond by Federal troops in April, 1865, near the end of the Civil War." Online Source: Carolana and the Incomparable Roanoke: Explorations and Attempted Settlements, 1620-1663 BY WILLIAM S. POWELL* [Vol. 51 (1974), 1-21]
I'm not sure if this is the same Henry Hartwell, but seems likely.
Maltravers was Henry Frederick Howard, who became Earl of Arundel after the death of his father Thomas. He had received the land originally granted to Sir Robert Heath by King Charles II and was working with Berkeley.