1st Feb 1990 to be precise. My records have them as a new operator at LTN in March 1988, which continued until their demise, using 1-11 400's. One of these was based although I cannot be sure of the time period, possibly both S88 and S89. 4 of the aircraft ended up being stored at LTN.
G-AXOX, G-AXMU, G-AXMG, G-AYWB 070490