"Affordable Online Maths Tuition" is a one-to-one tutoring programme where pupils receive maths tuition over the internet from trained maths graduates in India and Sri Lanka. It is delivered by the organisation Third Space Learning (TSL). Tutors and pupils communicate using video calling and a secure virtual classroom. Before each session, the pupils' normal classroom teachers are able to select lessons from TSL's maths curriculum to target individual learning issues. The intervention was targeted at Year 6 pupils who were working at Key Stage (KS) 2 level 3 or an insecure KS2 level 4, and was delivered over 27 weeks from September 2014 to May 2015 by (TSL) in an initial testing phase, with support from Nesta and Nominet Trust. The impact of the intervention was evaluated using a randomised controlled trial design, involving 64 schools and 600 pupils. Schools were randomised to either receive the intervention or deliver "business as usual" teaching, which might have involved intensive one-to-one support for maths. A process evaluation was undertaken to understand the perceptions of teachers and pupils, assess whether the intervention was delivered as intended, and inform any future development of the intervention. The evaluation should be considered an efficacy trial. Key conclusions include: (1) The impact evaluation found no evidence that the intervention had an impact on Key Stage 2 maths, compared with "business as usual" teaching and support in Year 6; (2) Teachers were largely positive about the online tuition, and reported that it appeared to improve pupils' comprehension, verbal fluency, and confidence in maths; (3) Schools should consider whether their computer network can support the implementation of an online programme. Teachers were positive about the technical support and user experience of the programme, but some experienced technical challenges in the implementation; (4) As the online tuition is a "talking" intervention, it appeared to work better when the pupils were spaced out in larger rooms so that the noise from other sessions was less distracting; and (5) Future research could examine whether the programme has an impact on pupils' comprehension, mathematical capacities, verbal fluency, and confidence in maths, as this was an outcome reported by teachers.