Arguable. It used to be the case that at the time of execution, the sheets must be attached in some way. That rule was relaxed to allow that holding the sheets together with finger and thumb was sufficient annexation. I have found a case where a second sheet contained only the attestation clause and signatures and the sheets were not attached in any way and probate was refused even though the first page was signed by the testator. It will depend on the precise facts though.
Personally, I wouldn't risk it. I say this for two reasons. Firstly, if your signature is on the last page only, there is nothing to stop someone replacing the first page with a forgery. Secondly and most importantly, it is likely to be challenged, if not by your family, but by the Probate Registry who can and do question wills. In order to prove validity, your witnesses will need to provide a statement. In 20 or 30 years time they may be dead, untraceable or unable to remember whether both pages were together. All this will not be without cost.
I'd take dzug's advice and redo it.