TootTootTootsie G.
Yelp
Construction of Castle Howard began circa 1699 and it took more than one hundred years to complete. Best known as the setting for the late-1970s television miniseries and the 2008 film "Brideshead Revisited," it attracts only 200,000 visitors per year, probably due to its somewhat remote location.
From London you can take British Rail to Malton and then either a cab (£10 one way) or the Castle Howard Shuttle Service, which departs from the bus depot opposite the railway station. Purchase of a House and Gardens ticket for £11.00 gives you access to the main building, four exhibitions, outdoor guided tours, a boat trip on the lake, a children's playground, six shops, and three cafés.
Alternatively, from York you can take a full-day tour that includes a four-hour stop at Castle Howard offered by the York Pullman Bus Company (see http://www.yorkpullmanbus.co.uk/TourDescription.aspx?ID=1&WebItem=2 for details).
The house and 1000 acres of landscaped gardens are magnificent, and there are extensive collections of artwork, porcelain, and sculpture to be seen. You really need several hours to do everything justice.
If it's a warm sunny day, I recommend you have either lunch or traditional tea on the patio of the Courtyard Café, which specializes in seasonal ingredients and features favorites like beef and ale pie, sausages with onion mash, Yorkshire pudding with gravy, and sticky toffee pudding.
If you have a sweet tooth be sure to visit the chocolate shop, where you can buy mouthwatering locally handmade candy. Locals might want to take advantage of the Farm Shop, which has butcher, seafood, and deli counters selling local meat, fish, and regional cheeses, plus freshly baked breads and cakes, preserves, seasonal fruit and vegetables, speciality teas and coffees, and wine and beer.
There's also a shop selling books covering a wide variety of interests, including local history, gardening, travel, cooking, and crafts.
Personally, I feel Castle Howard is worth a trek from London and a definite must-see if you already are in North Yorkshire.