There are two approaches, labelled “MtM” and “Off”, respectively corresponding to “mark to market” and “off market” (the latter formerly called smoothing). These are for “blend” alone.

MtM Assumption  The initial discount rate is now always the yield on EITHER long-term conventional gilts for fixed payments OR index-linked gilts for indexed payments. While simplistic, it is not only simple but also not that far away from what broadly tends to have been assumed.

Off Assumption  The expected return is estimated as a multiple of the initial yield, namely 2.26 for equities and 1.11 for conventional gilts. The historical results are charted here. For ILGs, I am still using “yield + expected long-term inflation + 1%” (taken from www.ukrpi.com).