You're right Harrymac. The notes from the time mention a large backlog of rifles awaiting backsights due to the complexities of production and '....this matter will have to be expedited in the shortest time'. I don't think that they ever speeded up the production of Mk5 backsights and as the Mk6/No4 was waiting in the wings in any case, the Mk5's went back into store, incomplete. And this is the reason why there are thousands of backsight-less Mk5's around. That WAS the case until EFD came to the rescue with their highly motivated 's--t or get off the pot' attitude.

As we say in Englandicon...... It's like shopping at Marks and Spencer. You get JUST what you pay for!