Inclusion Criteria:

• People aged 65 years and over who have diabetes complicated by one or more ulcers on a foot or both feet below the level of the malleoli, excluding ulcers confined to the interdigital cleft.
• Those with more than one eligible ulcer will have one – usually the largest or more clinically significant – selected as the index ulcer.
• Eligible ulcers will be hard-to-heal, meaning that the cross-sectional area will decrease by less than 50% during a four (4) week period prior to the first application of the 3C Patch® (percentage determined clinically by the treating physician by estimation at examination).
• Cross-sectional area must increase by less than 25% during a four week period prior to the first application of the 3C Patch® (percentage determined clinically by the treating physician by estimation at examination).
• The cross-sectional area of the index ulcer will be between ≥ 50 and ≤ 1000 mm^2 at the end of the 4-week period prior to the first application of the 3C Patch® (size determined clinically by the treating physician by estimation at examination).
• Participants will have the capacity to understand study procedures, and will be able to provide written informed consent.

Exclusion Criteria:

• Presence of sickle-cell anaemia, haemophilia, thrombocytopenia (< 100x10^9 /L) or other clinically significant blood dyscrasia.
• Known potential infectivity of blood products, including known HIV and hepatitis.
• Patient in dialysis.
• Clinical signs of infection of the index ulcer or reason to suspect that infection is present at randomization.
• Revascularization procedure in the affected limb undertaken within the 4 weeks prior to the first application of the 3C Patch® .
• Current treatment with cytotoxic drugs or with systemically administered glucocorticoids or other immunosuppressants.
• Treatment of foot ulcers with growth factors, stem cells or equivalent preparation within the preceding 8 weeks.
• The need for continued use of negative pressure wound therapy.
• Likely inability to comply with the need for periodic visits because of planned activity.
• Participation in another interventional clinical foot ulcer-healing study within 4 weeks of the first application of the 3C Patch® .
• Prior enrolment in this study.
• Judgement by the investigator that the patient does not have the capacity to understand the study procedures or provide written informed consent.