Well I had rather assumed that the OP did actually verify that it was his friend asking for this
Surely that's the first step you would take if you thought is was a scam, before WASTING THE TIME OF the world asking "is this a scam"?
Frankly, if he hasn't done this, I am very very annoyed with the OP for wasting my time, even if you are not.
Especially as 300 pounds seems rather a lot to be gifting to a niece of a friend. 20 pound seem more appropriate for that to me. So it seems reasonable to assume that there is some special reason for it being 300 pound that has been discussed by the OP and his friend.
only because you think that I am idiotic enough to act on an email message alone.
which I am most certainly not
AIH no
I haven't read it for ages.