Naturally Neil Simmons, the sculptor who created the statue from a 2-ton block of marble, has said he was "deeply saddened" at its beheading. The BBC reports that the statue was the result of eight months of sculpting work and that it took 2 years to identify a suitable block of marble.
The statue was commissioned by an anonymous donor in 1998, for exhibition in the Members Lobby of the UK parliament. The speaker of the House of Commons had changed the rules on exhibiting statues of still-living ex-Members and decided that the staue could be placed there 12 years of 3 parliament terms after Mrs. Thatcher had left office. This was due to take place in 2006.
My only comment is that it is unfortunate that the damage of a statue of a widely reviled public figure should be regarded as criminal damage rather than artistic expression in its own right. Perhaps the beheader of the statue should have waited until the statue was no longer private property before making his "modification" to the work. I'm sure a lot of people already approve of the modification and that this fact should mitigate any sentence against him for "criminal damage".