This ignores the fact that in many groups there will be inter-company guarantees and composit guarantees and debentures in favour of banks and other lenders, so if there is external borrowing every company in a group will be a guarantor of the borrowing of every other company. This will result in a holding company being hit by, say, an insolvency of one of the subsidiaries and triggering the Holding Company's need to appoint an Administrator.
No.
Whilst it is possible that cross guarantees and inter group loans of one company could cause the whole group to fail, for this to occur would amount to gross negligence by the Board.
In this case even if Shoreham had been operating at a loss it is inconceivable that the losses of Shoreham alone would cause the demise of the whole group.