Where to cut this oak to minimise stress on what remains

[SbTVF]

Farmers/Firewood merchant more than homeowners question here but... Big old 5 stemmed (possibly coppiced a long long time ago) oak and 2 of the stems are leaning heavily over a field edge so far that we haven't had a tractor under for years.

 

We'd like access but don't want to damage the tree if it can be helped as the remaining 3 stems are easily over 20" dbh and looking very healthy.

 

Pictures attached, where is the best place to cut please? In the second picture one stem is directly behind the other.

[SbTVF]

Rural or character grade perhaps. Look at the epicormic shoots. It's woodland edge.
Compare prices of oak posts from your local sawmill/supplier.
Milling may well be better than firewood
 

Oh yeah I meant mainly feature stuff for my own house/garden or 'rustic' mantelpiece type stuff. Wasn't expecting structural quality.