Inclusion Criteria:

          1. Histopathological/cytological diagnosis of non-resectable, recurrent or metastatic
             colorectal cancer

          2. Tumour with wild-type RAS

          3. Measurable disease evaluated by RECIST criteria v1.1

          4. WHO performance status 0 or 1

          5. Age ≥ 16

          6. Estimated life expectancy > 3 months

          7. Adequate haematological function:

               -  Haemoglobin ≥100 g/L

               -  Absolute neutrophil count ≥1.5 x 10^9/L

               -  Platelet count ≥100 x 10^9/L

          8. Adequate liver function:

               -  Total bilirubin ≤1.5 x upper limit of normal (ULN) (except for patients with
                  known documented cases of Gilbert's syndrome)

               -  ALT, AST & ALP ≤2.5 x ULN in the absence of noted liver metastases

               -  ALT, AST & ALP ≤5 x ULN in the presence of liver metastases

          9. Adequate renal function:

               -  Serum creatinine ≤1.5 x ULN

               -  Calculated creatinine clearance ≥30 mL/min

         10. Adequate biliary drainage (patients with stents are eligible)

         11. Adequate venous access for collection of exploratory biological samples

         12. Women of child-bearing potential must have a negative pregnancy test prior to study
             entry. Female patients and male patients with partners of child-bearing potential must
             agree to use an adequate contraception method, which must be continued for 6 months
             after completion of chemotherapy

         13. Must be able to swallow AZD8931 tablets

         14. Capable of giving written informed consent

         15. The following prior therapy is allowed:

               -  Surgery - patients may have undergone a non-curative operation or palliative
                  bypass surgery only. Patients who have previously undergone curative surgery must
                  have evidence of non-resectable disease relapse

               -  Radiotherapy - for localised disease

               -  Prior adjuvant chemotherapy - provided this was completed at least 6 months
                  before trial entry

        Exclusion Criteria:

          1. Patients undergoing treatment with curative intent

          2. Any prior treatment with agents targeting the ERBB pathway

          3. Treatment with experimental drugs within 30 days or 5 half-lives of first dose of
             AZD8931

          4. Previous palliative chemotherapy

          5. Prior treatment with anthracyclines or mitoxantrone

          6. Current disease or condition known to interfere with absorption, distribution,
             metabolism or excretion of drugs (including refractory nausea and vomiting, chronic
             gastrointestinal disease (e.g. inflammatory bowel disease), or significant bowel
             resection)

          7. History of prior malignancy that will interfere with the response evaluation
             (exceptions listed in protocol)

          8. Evidence of severe/uncontrolled systemic diseases or laboratory finding that makes it
             undesirable for the patient to participate in the trial

          9. Evidence of active uncontrolled infection

         10. Patients with clinically significant ascites and/or effusions

         11. Regular use of anti-diarrhoeal

         12. Pregnant or lactating women

         13. Cardiac conditions (as detailed in the trial protocol)

         14. Any psychiatric or other disorder (e.g. brain metastases) likely to impact the ability
             to give informed consent

         15. Eye conditions (as detailed in the trial protocol)

         16. Patients with chronic skin conditions e.g. acne rosacea, psoriasis, severe atopic
             eczema

         17. Past medical history of interstitial lung disease, drug-induced interstitial lung
             disease, radiation pneumonitis which required steroid treatment, or any evidence of
             clinically active interstitial lung disease

         18. History or repeated unexplained episodes of syncope/dizziness

         19. Known hypersensitivity to AZD8931, its excipients, or drugs in its class

         20. The use of drugs/substances known to inhibit or induce CYP3A4 or CYP2D6, or those
             known to prolong QT interval, which cannot be discontinued for the duration of trial
             treatment

         21. Patients with hereditary fructose intolerance