Exclusion criteria for ALL participants: 1. Previously hospitalised for COVID-19 infection 2. Previously referred to a long COVID clinic Exclusion criteria for nested, adaptive randomised drug trial: 3. Females who are pregnant, planning pregnancy or breastfeeding 4. Known hypersensitivity to any of the study drugs or their excipients 5. Currently taking any of the following drugs: probenecid, sucrafate, isocarboxazid, phenylzine, tranylcypromine of any other CNS depressant (such as diphenhydramine, dextromethorphan, or pseudoephedrine) (contraindications to famotidine/loratadine), amiodarone, aprepitant, atanazavir, atorvostatin, azithromycin, bezafibrate,ciclosporin, ciprofibrate, clarithromycin, cobicistat, croztibib, darunavir, diltiazem, dronedarone, eliglustat, erythromycin, fenobibrate, fluconazole, fluvastatin, fosamprenavir, gemfibrozil, idelalisib, imatibib, isavuconazole, itraconazole, ketoconazole, letermovir, lopinavir, netupitant, nilotinib, posaconazole, pravastatin, ranolazine, ritonavir, rosuvastatin, simvastatin, tipranavir, velpatasvir, vemurafenib, venetoclax, verapamil, voriconazole (contraindications to colchicine), acalabrutinib, aceclofenac, acenocoumarol, alprostadil, alteplase, argatroban, aspirin, axitinib, beniparin, benzydamine, bevacizumab, bismuth, bivalirudin, bosutinib, bromfenac, cabozantinib, cangrelor, caplacizumab, celecoxib, cilostazol, clopidogrel, cobimetinib, dabigatran, dalteparin, danaparoid, dasatinib, dexkeptorofen, diclofenac, dipyridamole, enoxaparin, epoprostenol, eptifibatide, etodolac, etoricoxib, flurbiprofen, heparin, ibrutanib, ibuprofen, iloprost, imatinib, indomethacin, inotersen, ketoprofen, ketorolac, levatinib, mefenamic acid, meloxicam, nabumetone, naproxen, nicotinic acid, nintenanib, parecoxib, pazopanib, phenazone, phenindione, piroxicam, ponatinib, prasugrel, regorafenib, ruxolitinib, sorafenib, streptokinase, sulindac, sunitinib, tenecteplase, tenoxicam, tiaprofenic acid, ticagrelor, tinzaparin, tirofiban, tolfenamic acid, trametinib, traztuzumab emtansine, trprostinil, urokinase, volanesorsen, warfarin (contraindications to rivaroxaban) 6. No history or presenting symptomology suggestive of renal failure/insufficiency (eGFR <30 ml minute) on the basis of blood investigations (eGFR) within the last 6 months and clinical assessment 7. Severe liver dysfunction on the basis of blood investigations within the last 6 months (liver function and coagulation) and clinical assessment

Exclusion criteria for ALL participants: 1. Previously hospitalised for COVID-19 infection 2. Previously referred to a long COVID clinic Exclusion criteria for nested, adaptive randomised drug trial: 3. Females who are pregnant, planning pregnancy or breastfeeding 4. Known hypersensitivity to any of the study drugs or their excipients 5. Currently taking any of the following drugs: probenecid, sucrafate, isocarboxazid, phenylzine, tranylcypromine of any other CNS depressant (such as diphenhydramine, dextromethorphan, or pseudoephedrine) (contraindications to famotidine/loratadine), amiodarone, aprepitant, atanazavir, atorvostatin, azithromycin, bezafibrate,ciclosporin, ciprofibrate, clarithromycin, cobicistat, croztibib, darunavir, diltiazem, dronedarone, eliglustat, erythromycin, fenobibrate, fluconazole, fluvastatin, fosamprenavir, gemfibrozil, idelalisib, imatibib, isavuconazole, itraconazole, ketoconazole, letermovir, lopinavir, netupitant, nilotinib, posaconazole, pravastatin, ranolazine, ritonavir, rosuvastatin, simvastatin, tipranavir, velpatasvir, vemurafenib, venetoclax, verapamil, voriconazole (contraindications to colchicine), acalabrutinib, aceclofenac, acenocoumarol, alprostadil, alteplase, argatroban, aspirin, axitinib, beniparin, benzydamine, bevacizumab, bismuth, bivalirudin, bosutinib, bromfenac, cabozantinib, cangrelor, caplacizumab, celecoxib, cilostazol, clopidogrel, cobimetinib, dabigatran, dalteparin, danaparoid, dasatinib, dexkeptorofen, diclofenac, dipyridamole, enoxaparin, epoprostenol, eptifibatide, etodolac, etoricoxib, flurbiprofen, heparin, ibrutanib, ibuprofen, iloprost, imatinib, indomethacin, inotersen, ketoprofen, ketorolac, levatinib, mefenamic acid, meloxicam, nabumetone, naproxen, nicotinic acid, nintenanib, parecoxib, pazopanib, phenazone, phenindione, piroxicam, ponatinib, prasugrel, regorafenib, ruxolitinib, sorafenib, streptokinase, sulindac, sunitinib, tenecteplase, tenoxicam, tiaprofenic acid, ticagrelor, tinzaparin, tirofiban, tolfenamic acid, trametinib, traztuzumab emtansine, trprostinil, urokinase, volanesorsen, warfarin (contraindications to rivaroxaban) 6. No history or presenting symptomology suggestive of renal failure/insufficiency (eGFR <30 ml minute) on the basis of blood investigations (eGFR) within the last 6 months and clinical assessment 7. Severe liver dysfunction on the basis of blood investigations within the last 6 months (liver function and coagulation) and clinical assessment