How to Remove 15mm to 22mm Converter from Old Shower Drainage and wastage systems and plumbing help, advice and answers

[themanalive]

I am probably being very stupid here, but I just can't work out how to remove a pipe fitting from an old shower I have just removed from my house.

The shower was attached to two pipes coming out of the wall. It came off easily, but there are what appear to be 15mm to 22mm converters (see image) screwed into the pipes. I would like to get them out but there is nothing to get the wrench onto. I know I will kick myself when someone points out the obvious way to do it, but please can someone enlighten me!

https://goo.gl/photos/knmVKT1UiAYnG7hy9

[lets have a look]

put a spanner on the 15mm nut and get some grips and carefully hold the 15mm thread and turn the spanner on the 15mm nut anti clockwise,can't tell if it's plastic or metal and you don't say if you want to use it again,but you can buy new,ask for a 1/2 x 3/4 nipple or take that one with you.