The Bank is currently making changes to the production process at its Debden plant in Essex so that varnish is applied after the numbering process.

It was found that not enough time was allowed for the serial number ink to properly harden before being packed.

The 200m notes are all being treated, at a cost of 250,000, by being stored at a higher temperature to cure the ink and they will be issued into circulation from 19 August.

The Bank has said that it can meet demand for 5 notes from old stocks and that any new 5 notes minus their serial numbers are still legal tender.