The remaining portal rather spectacularly props up the smaller section of the split capstone. The old archaeologists would have described the whole thing as ‘much deranged’.
This is what seems like the front when you first approach but is actually the north side of the tomb. The lintel and the drystone walling that it spans are both modern. The capstone, under the immense pressure of its own weight, is also fracturing on the perpendicular.