Tube workers are another group which is seen as vital to keeping London functioning.

BBC: Which workers are really key?

The action comes as the London Assembly Conservative group called for a ban on Tube drivers going on strike.

BBC: Piccadilly Line Tube workers balloted for strike action

So Dr Wildt's group is, for example, using a test-tube assay to measure hormone patterns in the faeces of endangered clouded leopards, and correlating these to behaviour under stress with a view to improving reproductive efficiency.

ECONOMIST: Endangered species

Balasubramanian's group has been pursuing a four-stranded version of the molecule that scientists have produced in the test tube now for a number of years.

BBC: 'Quadruple helix' DNA seen in human cells