This won't be for everyone but for the lucky ones (like me) who can take advantage it's a great deal, even if I say it myself!
1. If you hold an American Express Preferred Rewards Gold card (maybe others) check the offers section in your online account for a Morrisons.com spend £60 get £25 statement credit and click save to card.
2. Proceed to Topcashback and click through to Morrisons and create a new account then put £100 worth of shopping in your basket.
3. Checkout with voucher code VOU1935269 which gives £20 off a £100 spend (credit to omair for OP) and pay with your amex.
You should then receive £7.57 in your topcashback account and a £25 statement credit on your amex.
£100 - £20 - £7.57 - £25 = £47.43
Note: the voucher code expires at the end of December whilst the Amex statement credit offer expires 18th Jan.