M27 Christmas closure: what Portsmouth drivers need to know (dates, diversions, and how to avoid the worst delays)

A major Christmas and New Year closure is coming to the M27, and it is one of the most significant planned shutdowns on the south coast this winter.

Hampshire County Council and National Highways have confirmed the motorway will be fully closed in both directions between Junction 9 (Whiteley) and Junction 11 (Fareham) from 8 pm on Wednesday, 24 December 2025, until 4 am on Sunday, 4 January 2026.

That stretch matters to Portsmouth because it’s a key link for anyone travelling between the city, Fareham/Gosport, Southampton, the M3, and beyond, particularly if you’re heading out to see family, catching a ferry, or working shifts over the festive period.

Why is the M27 being closed?

The closure is to enable a critical stage of the M27 Junction 10 improvement scheme. The headline engineering job is installing a new four-lane-wide underpass using a “box slide” technique, essentially sliding a massive pre-built concrete structure into place beneath the motorway. The upside: it avoids many months of narrower lanes, reduced speeds, and repeated overnight works.

Which section is closed?

• M27 closed both directions: J9 (Whiteley) ⇄ J11 (Fareham East)

• From: 8 pm, 24 December 2025

• To: 4 am, 4 January 2026

The diversion route (and why it will be busy)

A signed diversion via the A27 will be in place. Officials are being blunt about it: expect significant delays, because that alternative route will carry a lot of diverted motorway traffic.

Portsmouth Hospitals University NHS Trust has also warned that diversion traffic is expected to be particularly busy between around 10 am and 4 pm each day, so anyone with appointments, visiting hours, or staff shifts should plan accordingly.

What this means in practice for Portsmouth

Even though Portsmouth itself is not inside the closure zone, the knock-on effects can ripple across:

• A27 east/west approaches (especially around Fareham and Portchester)

• A32 corridors (Fareham/Gosport direction)

• Routes feeding M275 / city access as traffic redistributes

• Peak travel days when the region is already under pressure (Christmas visits + Boxing Day trips + New Year travel)

Travel advice that actually helps

• If your journey doesn’t need the J9–J11 section, plan a route that avoids it entirely (sat-navs sometimes try to “clever” you back into trouble).

• Avoid the middle of the day where possible; late evening or early morning travel is often calmer than the 10 am–4 pm window flagged locally.

• Check live updates before you go, not just when you’re already stuck in it. National Highways’ travel updates and scheme pages are the most reliable sources.

Other M27 works to be aware of:

Separately from the Christmas closure, National Highways has also been running overnight slip-road closures in December on other parts of the M27 as part of surfacing/overlay work (with dates and times published in their project updates). That’s not the same thing as the full J9–J11 shutdown, but it can still affect planning if you’re travelling in the evenings.