Cannot figure this out for the life of me 
What date in the month should I make overpayments on my mortgage in order to maximise the benefits of overpaying? I gather it depends on when the interest is calculated?
These are my t's and c's:
"The interest rate is an annual rate. Interest
will accrue at the interest rate on the
mortgage debt on a daily basis based on
a 365 day year. Interest is debited to the
account monthly in arrears (calculated
on the number of days in the preceding
month) on each payment"
And "Payments made to reduce the mortgage
debt, including those that form part of the
monthly payment, will reduce the amount
on which we calculate interest from the
date payments are paid to the account.
Any interest which is not paid on the
relevant payment day will itself form part
of the mortgage debt and bear interest
from that payment day until it is paid."