These were operated by Cambridge Class 101s.
This measured 4 1/8" x 3" when folded.
Boston-Lincoln
Cambridge-Ipswich
Cambridge-St Ives
Cleethorpes-New Holland Pier
Doncaster-Cleethorpes
Grantham-Nottingham
Grantham-Skegness
Harwich-Manningtree
Hertford North-Huntingdon
Ipswich-Lowestoft
Lincoln-Cleethorpes
Lincoln-Sheffield
London-Welwyn Garden City
Norwich-Lowestoft
Norwich-Sheringham
Norwich-Yarmouth
Romford-Upminster
Royston-Cambridge
Sheffield-Cleethorpes
Sheffield-Doncaster-Hull
Sheffield-New Mills
Sudbury-Colchester
Wickford-Southminster
More lines will be added in the future!