Highclere Castle

Have you checked out their web site? http://www.highclerecastle.co.uk/visiting-us/opening-times.html
Looks like you would need to buy tickets in advance and they seem to sell out pretty quickly. They open March 30th but have sold out for Easter and May already. There may be hordes in the gardens but it looks like an orderly flow through the house at set times, morning then afternoon.

The castle is open only when filming or another group is using the site. Check the website & buy tickets early. Take the train from London (1hr) Paddington Station to Newbury. Well worth the trip!!

The above information isn't accurate, the castle has been open for 70 days a year for a long time, a lot of castles, large homes etc., open to the public for the revenue since its so expensive to run them. This year Highclere Castle is open around Easter, May bank holiday, spring bank holiday and summer Sunday-Thursday from July 14 to September 12th. Most of the dates are sold out, but there are 10 days available in August and 8 days in September. If you are going to be there around any of those days, hope on Highclere website asap and book tickets.

If you are big Downton Abbey fans, then yes the trip is worth it. We were there July 1st last summer and even though the website said the tickets were sold out, I just wanted to stop by and see the house exterior and gardens. Surprisingly, they let us into the castle too, even though it was "sold out" online. I found that the grounds were very uncrowded and the castle "tour" was very crowded - hordes of people is very accurate. There was no guided tour and they basically herded you through the hallways, only able to peek into the bedrooms. Am I glad I went? Yes. But my husband, who is not a DA fan, did not particularly enjoy it due to the massive crowds inside the house.

@Jennifer, that is good information regarding stopping at Highclere (even tho it says sold out), having the possibilities of getting in as you did.

The information on Highclere is incorrect. Just Google for details and you will have the information that you need.

I have already bought my tickets for August and they are sold out for lots of their open times already. Since Downton Abbey became popular they are not as affable to let folks in who don't have tickets. You should buy them now if you know what day you can visit.