While I agree it wouldbe very unlikely for a bank to require a capital top up on a standard principle and interest mortgage where payments are being met.
However it is a completely different story for interest only loan where the term of the loan tends to be a far shorter period.
Also where equity in the property has been used for business or other similar loans where regular review/renewal periods are very common and this is regardless if repayments are being met or not.
an example of this would be where a bank has lent up to say 80% of the equity in a property as security on a busness loan. It is not uncommon for these loans to have yearly reviews. If the equity in the property has fallen below a level the bank is willing to accept as security then or top up has to be made or the bank will not renew the loan period.
