The John de la Pole tomb in Wingfield church has his feet resting on a lion with a forked tail. Does the forked tail symbolize anything please?
It's worth noting that the lion with a forked tail (queue forchée) is on John de la Pole's heraldry, which you can see below. That shows the heraldry from his wife's family, quartered with the De la Pole heraldry he inherited. The lion originates on the Burghersh family heraldry -- De la Pole's wife, Alice, was the daughter of Thomas Chaucer who had married a Burghersh heiress.
(Yes, those Chaucers. Alice was Geoffrey's granddaughter.)
Now, regarding the meaning of the forked tail -- John Bossewell's Workes of Armorie (1572) had this to say:
(Source, and see the screen shot below.)
The lion rampant with forked tail is a traditional emblem of Bohemia, now the Czech Republic, first evidenced on the seal of King Vladislaus II of Bohemia granted by Emperor Frederick Barbarossa in the mid to late 13th century.
The forked nature of the tail is not meant to represent a mythical or unusual creature; rather it is to represent a moving tail, or a wagging tail if you will.