Not a magpie but a seagull.
Was walking along the river saw a seagull making its way towards me squawking loud, I didn’t realise it was to try and attack me, carried on walking and 2 others came squawking and a couple of them deficated near me also. No contact made, just flying very close to me. Very scary as I have a huge fear of birds. I’m sure it was just to protect a little one though.