Very obviously the usual absurd money-grubbing PCN we see far too often, as the traffic management benefits of whalloping you for less than one minute are nil.
You should therefore submit representations on the basis that your car clock showed a time of just after 16.00, so you entered the street. This contravention is what legal people call "de minimis", too trivial to be bothered with, but with councils keeping the money from PCN payments, they just cary on.
There is an adjudication somewhere in London Tribunals where the council were shot down in flames on issuing PCNs right at the end of a restriction period. There may also be guidance on this from London Councils, but others more "London" experienced will be able to point you in the right direction.
