Cirsium palustre Marsh Thistle CC DD N
This plant can be a very tall thistle up to 2 metres, although more typically 1 m tall. It does, as its name suggests, grow in boggy ground. If from a distance you can see these thistles growing in the field ahead, expect to squelch your way across. It is every bit as spiny as it looks. The flowers are usually purplish like most thistles but can be white.
C. palustre is found all over the British Isles and Ireland.