We had made plans to visit a friend in Chelmsford (about an hour northeast of London) for 4 days and have tickets to fly from London Stansted to Dublin. She recently had a stroke and won't be able to host us so we are looking for places to stay and/or visit not too far from Chelmsford so that we can visit with her at least one of the days. We have visited London twice and aren't really interested in spending more time there but could explore near London (we arrive at Heathrow) and then spend our last day or two near Chelmsford. We've spent time in Oxford, the Cotswolds, Bath, and some other places within about a 2 hour train or bus ride. We'll be using public transportation so suggestions for places we could reach by bus or train would be greatly appreciated. Thanks in advance.

Sorry about your friend. The obvious option would probably be Cambridge -- it is only about 45 miles from Chelmsford. The problem would be there is no direct rail service -- it would require Cambridge > Liverpool Street > Chelmsford and take more than 2 hours.

I'd maybe look at Colchester -- 35-45 minutes direct train to Chelmsford and good access to Norwich, places on the coast etc. Castle, museums, galleries, Roman sites.

Colchester for the castle, definitely. If you are up that way and have a car, you are near John Constable country, Flatford Mill, etc. Spend a night in Lavenham, one of the prettiest medieval villages in England and stay at The Swan Hotel. Lavenham was Godric’s Hollow in a couple of Harry Potter films.

Chelmsford Cathedral. https://www.chelmsfordcathedral.org.uk/
Essex Police Museum https://www.essex.police.uk/museum
Public transport in Essex.
https://www.visitessex.com/inspire-m...blic-transport
https://www.visitessex.com/coastal-p...travel/by-rail

The links were so helpful. Thanks so much for taking the time to provide them.