• Female patients aged ≥18 years

• ECOG performance status 0-2

• Histologically proven diagnosis of high grade serous or high grade endometrioid carcinoma of the ovary, fallopian tube or peritoneum

• Most recent regimen must have included platinum (cisplatin or carboplatin)

• Must have previously received a PARP inhibitor

• 6\. Must have responded to most recent platinum treatment by CT or MRI or by GCIG CA125 response criteria

• Pre-trial CT or MRI-confirmed disease relapse ≥ 6 months after day 1 of the last cycle of platinum-containing chemotherapy (cisplatin or carboplatin) and requiring treatment with further platinum-based chemotherapy

• Measurable disease by RECIST v1.1 on a CT scan conducted within 28 days prior to randomisation (Patient with non-measurable disease could be eligible if they meet GCIG CA125 progression criteria)

• CA125 ≥ 100iU/l at screening

⁃ Agree to provide additional research blood samples at the same time as blood draws prior to each carboplatin treatment, 6-weekly during surveillance and at 12- weekly follow-up visit

⁃ Expected to be able to commence treatment within 28 days post randomisation

⁃ Adequate bone marrow function

⁃ Adequate liver function

⁃ Adequate renal function

⁃ Postmenopausal or women of child-bearing potential (WOCBP) must agree to have an urine or serum pregnancy test at screening for evidence of non-childbearing status and prior to trial treatment and use adequate contraception for duration of trial

⁃ Willing and able to give consent and able to comply with treatment and follow up schedule