The pole next to it. At the top is it vaguely like this? Both are phone masts
Notice in the photo next to the mast is green boxes looking just like the ones you've taken pics of.
If so it's a mobile phone mast (as has been suggested) and that green box is for whichever mobile network company is operating the telephone mast.
Edited by ukhardy07 (Thu 13-Sep-12 02:37:06)