for late joiner
The 2004 Finance Act put paid to pensions before age 55 so AFPS 05 ( which would the the scheme for new entrants going forward) could not be designed with an Immediate Pension. However, MOD needed something to pull people through to about age 40 and to compensate them as most people do not get to serve to 55. Thus the EDP was born and is part of a completely separate scheme.