A former commander of the Royal Anglians in Afghanistan thinks that the withdrawal of western forces from that country could have helped prompt Russia's invasion of Ukraine this week.

Colonel Richard Kemp retired from the Army 15 years ago and now lives in Essex from where he has become a regular commentator on military and security issues.

He said: "I think President Putin will have seen that withdrawal as a sign of weakness and that might have persuaded him to go ahead with this invasion."

Col Kemp did not think there was any likelihood of NATO sending in troops to Ukraine - but he did feel it was necessary to strengthen forces in the eastern European countries that were now members of the alliance.

"We have troops in Estonia and we are strengthening the NATO forces in Poland. I hope that the events in Ukraine will persuade the UK government to reverse the decision to cut back on defence that was seen in the latest review."

Although Col Kemp does not see any likelihood of sending in troops to Ukraine, there is a risk of direct conflict with Russia if there is an airlift of military supplies to the country through an "air corridor" which may have to be protected from hostile aircraft or missiles.

And he is very uncertain about the future outlook for Ukraine: "If the Russians do succeed in invading the country and installing a puppet state they could face the kind of guerrilla warfare we have seen in Chechnya or Afghanistan - with a lot of Russian casualties."

He believes President Putin would like to set up a client state in the country like the government in Belarus - but thought it was unlikely that a country that had had democratic freedoms for several decades would accept that.

And while the greatest focus is on events in Ukraine itself, there will be economic effects felt across Europe and the world.

Col Kemp said: "We have already seen increases in the cost of gas and other energy and this pressure will continue and increase - but I don't expect to see our troops involved in Ukraine itself."