I have owned a 14 year old Toyota Yaris from new, it has covered just 45,000 miles. Until recently it has been regularly serviced by my Toyota dealer and has always given reliable service.

A month ago a trusted, local garage changed the front discs, pads and wheel bearings. Since then my brakes have failed completely on more than half a dozen occasions, most fortunately each time I was either driving on an incline or able to stop by driving onto a grass verge.

Pumping the pedal makes no difference. Driving off after a few minutes the brakes appear to function normally. I have returned the vehicle to the garage twice, they have striped it down, tested it and can find nothing wrong. What do you think might be the cause if this intermittent brake failure?