Bosses have issued a plea for people to put a stop to their bad behaviour, warning that anyone who abuses its team will be asked to leave.
A spokesperson said: “We are sad to report that we are currently experiencing a high volume of verbally abusive behaviour towards our stewarding staff.
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"We appreciate that your visit to Alnwick Castle will feel different this year - there are new procedures in place and some areas cannot be accessed.
“We understand visitors may be frustrated, but we cannot excuse abusive behaviour towards staff or other visitors.
”We hope all our visitors understand our current opening measures are in place for their safety, and that of our staff, during the challenging times we still live in.
“Abuse is not acceptable.
"If any visitors engage in this type of behaviour, our security team may ask you to leave the grounds.
“All the information about our new procedures can be found on our website or in your booking confirmation email.”
Measures put in place include visits only via booking – no tickets are available on its entrance – with just its Greenwell Gate entrance next to Alnwick Garden open and stewards on hand to greet and direct guests.
Contact details are taken as part of the NHS Test and Trace scheme, with only The Inner Bailey, Outer Bailey, The Courtyard, The Coach House and the Bowburn Picnic Area outside the castle walls open and State Rooms accessible via guided tours only.
Entry to its museum is restricted due to social distancing, with only one family at a time allowed in and visitors asked to wear masks while in the tower.
The Constable's Tower, Café, Fryery Chip Shop, Castle Shop, Artisans Courtyard, the Dungeon, the Ramparts Walk and The Fusiliers Museum of Northumberland are closed, as are its main toilet facilities, with temporary loos near the entrance.