I was intrigued to read about London & County failing in 1973 and wondered if London & County Mortgages had any connection to them ?
"But it has been more than a century since any major bank went bust. Overend, Gurney & Company failed in 1866.
More recently, the secondary bank London & County failed in 1973 and Barings Bank had to be rescued in 1995, when it was bought for £1 by the Dutch giant ING. Grays Building Society was the most recent collapse in that sector, back in 1978."
Found some other info. here, which doesn't really help -