John Clare had a twin sister, but she died shortly after birth. (Source.)
John Clare escaped from High Beech asylum in 1841 (his first stint), and walked 80 miles back home. It took him four days! (Source.)
Since Clare was considered a "harmless" patient, he was allowed to leave the grounds of the Northampton Asylum. He used to sit in the portico of All Saints Church and write poetry. (Source.)
In the 1840s John Clare claimed he was an eyewitness to the execution of King Charles I, which took place in the 1640s! (Source).