Upvote:5
Yes, both visas are valid, but be aware that they don't have contiguous validity dates. So you must depart the UK on or before the end of the day 3 April, and cannot return until 10 April.
If your previous visa had been cancelled, it would have had a cancelled stamp placed on it, as in this example:
If your old visa has those stamps, then only your new visa is valid. Otherwise, both visas are valid.