Thanks all for your responses. It's just in our back garden in Surrey. It is south facing and the weather is scorching at the moment so that may explain the bloom. We've just moved in to this house and inherited this lovely garden so I don't know how this plant usually fares. I will do my best to look after it! Thanks all.

YAY!!!! Thank you. Now just have to read up on how to root the cuttings.

The HOA should have put a lien on the sale of the property from the last owner three years ago, I'd think and collected when the house sold if the previous owners had refused to remove it prior to the sale. Is there any way you can tell from association minutes if they had notified a previous owner to remove it? I am not up on trees out of my zone, but I can tell you for sure it isn't a sycamore. If it is a 'pepper tree' and you didn't plant it, my only other suggestion is to discuss this with an attorney who is versed in these types of contractual agreements. Oftentimes the initial consultation is at no cost, and should tell you right up front if you have no recourse to fight it. If you do have a chance of fighting it, you may also want to know if the previous owner had issues with the HOA and may have failed to disclose this when selling.

Thank you JonCongaroo I believe that you have it