If the M&S returns portal has not been functioning since before Christmas, there are several steps you can take to move forward with your return process:

1. Check M&S Returns Options: Visit the M&S Returns and Refunds page. This resource outlines various methods for returning items, including direct returns to stores, which could be the fastest option if the online portal is down - learn more.

2. Use the Mobile App: If you have the M&S app on your mobile device, you may be able to initiate returns through the app. Ensure you have the app updated to the latest version for the best experience - learn more.

3. Visit Local M&S Stores: You can return your items directly at any local M&S store, including Foodhalls. This is often the quickest way to process your return as it bypasses the portal entirely - learn more.

4. Contact Customer Support: If the above solutions do not work, you may want to contact M&S customer support directly for assistance. They can provide information and resolve issues regarding the returns portal - learn more.

5. Social Media Updates: Check M&S’s social media accounts for any announcements regarding the returns portal. Companies often post updates about technical issues or service interruptions on platforms like Twitter or Facebook.

6. Alternative Return Methods: While waiting for the portal to be fixed, see if you can generate a returns label through postal services like Evri, as mentioned in the return policies - learn more.

Following these steps should provide a comprehensive approach to completing your M&S return while the online portal is down.