This is the helmet we using now.
The Geman helmets we used in the ww2.In the 1930s early ,Our govts had been set up military alliance with the German .So you could see that helmets.
The Irish Army wore German style helmets too, they couldn't get them from Germany because of the ban on German military exports, so Vickers in the UK made them! They changed to British helmets around '40.