I think that, if it was at the end of your day, you can get away with a short 15 min drive over your time, to make a delivery and park up. If you are caught in an unforseeable delay. You need to write a brief explanation on the back of your chart and sign it.
The unforseeable bit is important. If for eg, you were caught in the usual M6 cluster[zb] at say ‘the waterjump’, that would not be a reasonable excuse as it happens every day and is therefore foreseeable.