The Ilford 2 Fixer Bath method also works for the 1+4 option (2 x 30sec with a rinse in-between to reduce carry over)
As Doremus has written in the above post, for Archival Processing, the 2 Fixer Baths gives much greater capacity per Litre of working Fix.
Ilford's no longer promoted Archival Processing
Originally Posted by Martin Aislabie
sequence with the one minute fix claimed a capacity
of 40 8x10s per liter of working strength. The 5-10-5
minute wash- hca- wash after fix sequence then
left in the paper archival levels of fixer.
IMO it was no more than the quickest way to
fix and wash A print to archival standards. The
method required a constant flow of water and
little interrupted attention. Not a very
practical way to process. Dan