I have two silver birch trees side by side (about 3 ft apart). There is a small block of flats next to our house and last summer a resident from that block took it upon themselves to lop my silver birches. They cut the upwards growing trunks (which were about 3 inches diameter) clean across at a height of about 10 feet from the ground. This left only the smaller branches which were growing out sideways from just below this point. I am looking for ideas as to how to (a) make sure the trees survive, and (b) encourage the lower branches to growupwards to replace the shape and coverage lost from the main trunk. Any advice gratefully received.

Short answer: consult a qualified professional arborist about any
further trimming these two trees may need.

Longer answer: they will survive, and may do very well, especially
if the cut is directly above the branches. No stump sticking up?
Often the stump will die back to the union (where the branches are)
and the tree will try to cover the stump from the union upward.
Cutting the stump flush with the union helps the tree cover the
wound before significant rot sets in.

Two trees 3 feet apart is not ideal. Consider removing the weaker
one.

Una

Many thanks for the advice Una