These Health Authorities were established in 1996. There were a few changes between then and the final form shown above. There were originally separate authorities for Barnet and Enfield & Haringey, for Bexley & Greenwich and Bromley, for East & North Hertfordshire and South Hertfordshire, and for the Isle of Wight & Portsmouth and South-East Hampshire.  Also, the area of Norfolk and Cambridgeshire was partitioned between three authorities : Cambridge & Huntingdon, East Norfolk, and North West Anglia. North West Anglia included from Cambridgeshire: Peterborough, Fenland, part of Huntingdonshire, and from Norfolk: King's Lynn and West Norfolk and part of Breckland. 
Also, "East Riding and Hull" was originally known as "East Riding", , "County Durham and Darlington" was originally known as "County Durham"