Goofs

The corned beef tins in the Post Office are clearly labeled 'Pemmican', which is nonsense - Pemmican is something quite different (a greasy Native American concoction). In the book the children call corned beef 'Pemmican' ( and lemonade 'grog') to add to the feeling of having an adventure.

The film opens with the legend '1935', but as the Jackson family run for the train the sign boards are headed 'British Railways'. The 'Big Four' railway companies were not amalgamated into BR until 1948.

Mr Jackson (Harry Enfield) is frequently shown with a pipe in his mouth yet the pipe never appears to never be lit as we do not see him puffing on the pipe or smoke arising from it. Whilst this could be said to show a 21st century sensibility towards smoking in a childrens film we do however see a character smoking a cigarette at Portsmouth railway station earlier on.

When the kids travel to the island, they drop a basket of supplies into the lake. It included their matches. However, after they set up camp, they're seen reading at night by lamplight. Without matches, they couldn't have lit the lamps.

The film takes place during the 1930s, but the livery and insignia of the steam locomotive that takes the children to the Lake District is that of British Railways (BR), which didn't exist until the nationalization of the railways in 1948.

At 44:40, Andrew Scott is looking through his binoculars while some tiny bugs crawling on his wrist and he doesn't even seems to notice them or feel them but they look creepy.

Gunnera manicata, known as Brazilian giant-rhubarb, is a native to South America, yet is clearly visible on the island when the children confront the Russian agents. It is highly unlikely to have been planted on a remote island in the middle of the Lake District.

In the film's title sequence as the Walker family travel north, the children's map of their train journey shows that a huge lake over 100km across has appeared between the cities of Birmingham and Chester, somehow drowning the Midlands Plateau.