For HERA:


First ideas: 1981.

PEAS workshop: 1982.

Spin rotator designs: Buon and Steffen, and Barber et al. 1982---1985
===> dipole variable energy and geometry ``Mini Rotators'' chosen.

1985: Spin matching for 4 pairs of rotators with a civilised optic demonstrated (Barber).

``Transverse'' (West area) polarimeter designed and installed: 1988---1991.

First measurements 1991: about 8 percent vertical polarisation.

Better ring alignment and ``harmonic bumps'' 1992: over 60 percent.

Winter shutdown 1993---1994: installed one pair of rotators for HERMES in the East.

May 1994: first run with a pair of rotators: immediate success

1994 --- September 2000: routinely running with over 50 percent even with high proton current making beam--beam interaction in N and S.

1996: ``Longitudinal'' (East area) polarimeter designed and installed.

Then ~Nov. 1996: high proton currents ===> first indications of beam--beam effect on electron/positron polarisation.

September 2000 --- summer 2001: modifications for the HERA Luminosity Upgrade.

February 2003: first run with 3 pairs of rotators (N, S,,E) and the upgraded interaction regions and optic. 50 percent attained with the uncompensated detector solenoids switched on and with luminosity.

July 2008: HERA was switched off.