A Partial Rebuild
This resets the stones on the east side and the returns on the north and south sides only. The east side has the most movement and is the most obvious area to reset the steps. The returns to the north and south would also have to be reset on a new mortar foundation as well as the east side.
The remainder would be consolidated in place with only one area on the south-west corner bottom step to be reset.
Through this method, the worst of the slumped fabric would be reset, leaving the west side consolidated but still with slightly uneven steps. Thus the side of the monument facing the path to the church and seen by most visitors would retain the uneven appearance that has become part of its character. It would allow a complete archaeological investigation to explore the east side whilst leaving the west side mostly intact.
West side of monument
All joints will be raked out and cleaned; all earth and plant debris will be carefully removed to avoid damage to the stone core.
Mortar will be placed as deeply into the joints as possible; loose stones forming the core will be lifted and re-bedded in mortar, where possible in the position in which they were found.
The final pointing layer will be full and flush and match, as far as possible, the level of stones to either side.
East side of monument and south-west corner
Those stones which are to be removed and rebuilt will be agreed in advance with Historic England / the commissioned conservation-accredited architect
Stones forming the steps will be numbered and the numbers marked on photos/drawings to ensure that they can be replaced in the correct position.
The stones will be laid out around the pedestal in the order that they are removed, to ensure they can be correctly replaced. (All sides of the stones will be examined by the archaeologist, as they are removed, for any evidence of re-use, decoration, etc.)
After removal of the stone steps, the core will be recorded and archaeologically excavated by hand by the archaeologist: if any significant remains are encountered, work may be held up while these remains are recorded. The positions of any large or significant stones will be recorded in case they can be replaced in the same position.
The ground beneath the plinth will be excavated by the archaeologist to the depth required to construct a new mortar plinth to rebuild the steps up from. This depth will be advised by the architect.
A new foundation of mortar (what sort??) will be laid to the exact size of the cross pedestal. This should not be visible once the reconstruction is complete.
On reconstruction, the stones of the steps will be re-laid in the positions from which they came, bedded in lime mortar.
The core will be built up simultaneously with the steps (using what if the core has largely disappeared???)
Once rebuilt, the steps will be repointed. The final pointing layer will be full and flush.