There are two Long Cairns on the SMR in Northumberland, I believe, but both have a rounded plan. Please don't say 'there are none'. What you have seems to be an eartwork of some kind. Until you begin to understand the superstitions of the builders you'll not make much progress interpreting the features you discover.

The large stone pictured, with the female figure before it, is an erratic. But it's been stood on end and securely bedded. The carved grooves, at the top, prove that. Therefore it's a Standing Stone - and should be listed here as such. The Park archaeologists - I can dig out there contact details - should be told.

An accurate plan of these sites would be helpful - don't forget to include the extra bits from The Mare and Foal. Discovering (what-seems-to-be) the UK's tallest standing stone is quite an honour. One of the stones in the Langley stone circle is reported to have three boat-shaped cupmarks - a picture of these would be handy ...