Bramley apple disease

One trunk ( main trunk divides into three a metre above ground) of an old bramley tree looks as though a coppery solution has been poured down it, reaching to ground level. Another trunk has lost a lot of bark but the third is normal colour and bark cover. the damage is on south east side of tree mostly. We live in the fens so are exposed to the wind. Can anyone help please? We would hate to lose the tree but have failed to find a diagnosis.     Many thanks.