Building work on a £15m project to create Europe’s leading teenage cancer treatment centre has reached a milestone.

Patients and staff at the Royal Marsden Hospital joined construction workers to witness the highest brick being put in place on the new children and young person’s centre.

The Royal Marsden’s director of projects Colin Rickard used a silver trowel to commemorate the event, known as a topping out ceremony.

When the first part of the centre is completed in July this year, the existing children’s unit will be refurbished to provide outpatient and day care facilities. The new unit means teenagers will not have to be treated alongside toddlers or the elderly.

Patient Rachel Belshaw, 13, said: “I think it will help lots of children like me feel more homely while they are having treatment and give us more space to chill out.”

The second phase of the project is scheduled for completion in February 2011.

The centre will have a pioneering drug development centre, to enable anti-cancer agents to be tested on site for the first time.

The building will have green elements including solar shading on the south and west sides, 400sq metres of photo voltaic cells on the roof to help generate energy to run the centre and rainwater will be collected and used for flushing toilets.