Sad to relate, the Mk III that was on display in Haslingden (Lancashire, U.K.) does not now appear to be buried beneath Victoria Park.
According to this newspaper article it was broken up.
"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
Needs a log in to see the webpage you've linked to.
heres the article in question not much but pretty clear...
http://2.bp.blogspot.com/-82rx2p2Gq9E/TjzxRz9o9-I/AAAAAAAAEkQ/NKbN5SKhGgQ/s1600/tank.JPG
from this site...
http://haslingdens.blogspot.com/2008/11/what-became-of-our-ww1-mkiii-tank.html
Cheers
"Ash nazg durbatulûk, ash nazggimbatul, ash nazg thrakatulûk, agh burzum-ishi krimpatul"
Â