Facebook is planning to test pre-roll ads which will appear before shows on its Watch video service, according to a report in AdAge.

Watch launched in August with mid-roll ads (in the middle of shows) but to date, Facebook has studiously avoided running pre-roll ads. As thr AdAge story notes, as recently as July, Facebook CEO told investors on a conference call: “We dont need to do pre-roll because our model is not one where you come to Facebook to watch one piece of content, you come to look at a feed.”

But Watch is different. Designed as a rival to YouTube, it’s more akin to watching traditional TV than scrolling quickly through a news feed, hence the rumoured change in approach.

Separately, today sees the opening of Facebook’s new London office, together with a pledge from the company to create 800 new jobs in the UK in 2018, bringing the total number of UK Facebook employees to 2,300.

The new office in Rathbone Place will be home to Facebook’s first in-house start-up incubator called LDN_LAB. This will invite UK-based start-ups to take part in three month-long programmes designed to help kick start and accelerate their businesses. The programme will help start-ups who are focused on creating, building or empowering communities through innovation and technology.

Facebook experts from a range of disciplines including engineering, product and partnerships, will share their knowledge, expertise and mentorship as part of the programme. The London site will be Facebooks biggest engineering hub outside the US.